In this work, the authors report on the observation of heteronuclear ultralong-range Rydberg molecules, together with a detailed theoretical analysis of the experimental data. Such heteronuclear Rydberg molecules are expected to present many new opportunities for studying quantum systems, such as probing interparticle and interspecies pair correlation functions in multicomponent many-body systems, exploring the sensitivity of the isotope shift to the mass polarization energy for Rydberg trimers or larger molecules, or studying new types of Rydberg impurities in quantum gases.

[Phys. Rev. A 101, 060701(R)] Published Wed Jun 24, 2020

A recently developed model to describe proton collisions from molecules involving basic atoms such as hydrogen, carbon, nitrogen, oxygen, and phosphorus (H, C, N, O, P) is extended to treat collisions with multiply charged ions. The ion-atom collisions are computed using the two-center basis generat…

[Phys. Rev. A 101, 062709] Published Mon Jun 22, 2020

We present the energy and angular distributions of electron emission from a ${\mathrm{CH}}_4$ molecule in collisions with fast bare C ions with energies 3.5 and 5.5 MeV/u. The absolute double differential cross sections (DDCS) are measured for the ejected electrons having energies from 11 eV to 330 eV for $3.5-\mathrm{MeV}\dots$

[Phys. Rev. A 101, 062708] Published Wed Jun 17, 2020

By using a nonequilibrium approach based on real-time time-dependent density-functional theory combined with molecular dynamics simulations, the effects of $d$-electron excitation on the electronic energy loss of energetic protons colliding with atomic zinc target are studied. The results show that th…

[Phys. Rev. A 101, 062705] Published Thu Jun 11, 2020

Charge-state selective recombination rate coefficients were measured by time of flight (TOF) analyzed highly charged Si ions extracted from an electron-beam ion trap. Additionally, the combination of simultaneous TOF and x-ray measurements and a separation of the dielectronic recombination contribut…

[Phys. Rev. A 101, 062706] Published Thu Jun 11, 2020

We study double ionization of Mg by electron impact through the vantage point of classical mechanics. We consider all electron-electron correlations in a Coulomb four-body problem, where three electrons belong to the atom and the fourth electron causes the impact ionization. From our model we comput…

[Phys. Rev. A 101, 062707] Published Thu Jun 11, 2020

We present a theoretical investigation of the radiative recombination of twisted electrons into bound states of initially bare ions. Special emphasis is placed on the magnetic sublevel population of the residual hydrogenlike ions under the assumption that emitted photons remain unobserved. We show t…

[Phys. Rev. A 101, 062704] Published Thu Jun 04, 2020

${}^3\mathrm{He}$ beam spin-echo experiments have been used to study surface morphology, molecular and atomic surface diffusion, phonon dispersions, phason dispersions, and phase transitions of ionic liquids. However, the interactions between ${}^3\mathrm{He}$ atoms and surfaces or their adsorbates are typically isotropic and …

[Phys. Rev. A 101, 062703] Published Tue Jun 02, 2020

The stopping power of protons through Hf foil has been studied both experimentally and theoretically. The measurements were performed at the Laboratory of Accelerators and X-Ray Diffraction in Lisbon by using the transmission method on self-supporting stopping material. The overall uncertainty of ar…

[Phys. Rev. A 101, 062701] Published Mon Jun 01, 2020

We study three-body recombination of fully spin-polarized ${}^6\mathrm{Li}$ atoms that are interacting resonantly in relative $p$ waves. Motivated by a recent experiment, we focus on negative scattering volumes where three atoms recombine into a deep dimer and another atom. We calculate the three-body recombination…

[Phys. Rev. A 101, 062702] Published Mon Jun 01, 2020

We present calculations of electron scattering from ${\mathrm{BeH}}_2$ using the $R$-matrix method. Integral and differential elastic and inelastic cross sections for energies up to 20 eV have been determined and the position and width (when possible) of shape and core-excited resonances is reported. The use of Gau…

[Phys. Rev. A 101, 052709] Published Thu May 28, 2020

The spin-dependent interactions (SDIs), consisted of second-order spin-orbit coupling (SOC) and magnetic dipole-dipole interactions (MDDI), play an important role in ultracold two-body collisions for heavy atoms. We survey the inelastic two-body loss induced by SDIs in ultracold collisions of ${}^{85}\mathrm{Rb}$ i…

[Phys. Rev. A 101, 052710] Published Thu May 28, 2020

The charge relaxation of accumulated charge patches in insulating straight capillaries is investigated theoretically. The model assumes that charges accumulate only at the inner and outer insulator-vacuum interface of the capillary but not in the bulk. We give an analytical solution to the coupled e…

[Phys. Rev. A 101, 052707] Published Wed May 27, 2020

The charge-transfer process for collisions of ${\mathrm{C}}^{4+}$ with atomic hydrogen is studied theoretically and experimentally in this work. Our theoretical study is based on an electron-nuclear dynamics approach applied here for the state-to-state and total contributions to the electron-capture cross sections.…

[Phys. Rev. A 101, 052708] Published Wed May 27, 2020

Photoelectron satellite spectra and angular distribution of argon atoms were measured in the energy range of 34–43 eV, using a well-developed reaction microscope mounted on a newly built high-order harmonic generation (HHG) extreme ultraviolet (EUV) source. Various satellites were resolved and the a…

[Phys. Rev. A 101, 052706] Published Tue May 26, 2020

We investigate the fragmentation dynamics of a hydrogen atom impacted by a positron whose energy is just above the atomic ionization potential (i.e., near threshold), using a classical trajectory Monte Carlo approach with a Heisenberg potential (CTMC-H). The cross sections of various fragmentation c…

[Phys. Rev. A 101, 052704] Published Fri May 22, 2020

Fully quantum ab initio calculations of the collision-induced shapes of two rovibrational ${\mathrm{H}}_2$ lines perturbed by He provide an unprecedented subpercent agreement with ultra-accurate cavity-enhanced measurements. This level of consistency between theory and experiment hinges on a highly accurate poten…

[Phys. Rev. A 101, 052705] Published Fri May 22, 2020

The electron-impact double ionization (DI) and triple ionization (TI) for O ii-iv ions are investigated using multistep approaches within the framework of many-body perturbation theory. The indirect DI and TI are treated as the single ionization of an inner-shell $1s$ electron followed by the single a…

[Phys. Rev. A 101, 052703] Published Wed May 20, 2020

We calculate the isotope-independent ${\mathrm{Li}}^{+}$-Li potential energy curves for the electronic ground and first excited states. The scattering phase shifts and total scattering cross section for the ${}^7\mathrm{Li}^{+}\text{−}{}^7\mathrm{Li}$ collision are calculated, with an emphasis on the ultralow-energy domain down to the $s$-wave regime. …

[Phys. Rev. A 101, 052702] Published Mon May 11, 2020

The three-body fragmentation dynamics of triply charged allene (${\mathrm{CH}}_2{\mathrm{CCH}}_2^{3+}$) induced by 50-keV/u ${\mathrm{Ne}}^{8+}$ ion impact is studied by measuring the charged fragments in coincidence using the reaction microscope. We focus on the fragmentation dynamics of two completely measured fragmentation channels, ${\mathrm{H}}^{+}+{\mathrm{CH}}^{+}+{\mathrm{\dots }}_{}$

[Phys. Rev. A 101, 052701] Published Mon May 04, 2020

In the present study we have investigated the ionization threshold behavior of neon cluster ions ${\mathrm{Ne}}^{n+}$ (with $n=2-6$) formed upon the electron ionization of small neon clusters. The clusters were formed by supersonic expansion of cold neon gas through a pinhole nozzle. The appearance energies for these…

[Phys. Rev. A 101, 042708] Published Tue Apr 28, 2020

The three-body recombination rate coefficients of the $\mathrm{H}+\mathrm{H}+\mathrm{H}\to {\mathrm{H}}_2+\mathrm{H}$ process for different final rovibrational levels of ${\mathrm{H}}_2$ are determined using a fully quantum-mechanical approach at zero total angular momentum. The Jahn-Teller coupling between the lowest electronic states of the ${\mathrm{H}}_3$ system is accounted…

[Phys. Rev. A 101, 042709] Published Tue Apr 28, 2020

We consider nonradiative annihilation of a positron on electrons bound by the field of a heavy nucleus. This process proceeds via the interaction of the annihilating positron-electron pair with another bound electron which is emitted carrying away the energy release. We present a fully relativistic …

[Phys. Rev. A 101, 042707] Published Mon Apr 27, 2020

The dynamics of four-body Coulomb explosion of acetylene in collision with 50 keV/u ${\mathrm{Ne}}^{8+}$ are investigated by detecting all four ionic fragments and the scattered projectile in quintuple coincidence. Six different breakup channels of ${\mathrm{C}}_2{{\mathrm{H}}_2}^{q+}$ cations with $4⩽q⩽8$ are identified. The kinetic energy (KE) d…

[Phys. Rev. A 101, 042706] Published Wed Apr 22, 2020

High-precision quantum-mechanical calculations have been developed to investigate positronium (Ps) scattering. Positronium scattering experiments are a powerful tool to study positronium-matter interactions, but the theoretical description of these experiments needs better accuracy. We have develope…

[Phys. Rev. A 101, 042705] Published Tue Apr 21, 2020

We create weakly bound bosonic ${}^{23}{\mathrm{Na}}^{39}\mathrm{K}$ molecules in a mixture of ultracold ${}^{23}\mathrm{Na}$ and ${}^{39}\mathrm{K}$. The creation is done in the vicinity of a so far undetected Feshbach resonance at about 196 G which we identify in this work by atom-loss spectroscopy. We investigate the involved molecular state by performing d…

[Phys. Rev. A 101, 042704] Published Mon Apr 20, 2020

A coupled-channel model is developed to analyze the interaction energy shift of ultracold lithium atoms in a Mott insulator state. This refined treatment shows a better agreement with the experimental data than the standard Hubbard model.

[Phys. Rev. A 101, 042703] Published Wed Apr 15, 2020

Ultracold polar molecules can be shielded from fast collisional losses using microwaves, but achieving the required polarization purity is technically challenging. Here, we propose a scheme for shielding using microwaves with polarization that is far from circular. The setup relies on a modest stati…

[Phys. Rev. A 101, 042702] Published Mon Apr 06, 2020

We have measured characteristic $K$ x rays in coincidence with the scattered particles from collisions of hydrogenlike Ge ions with Kr atoms. The ions were first accelerated to 8.6 MeV/amu, post-stripped to H-like charge state, and decelerated to around 2.5 MeV/amu. From the measurements the probabili…

[Phys. Rev. A 101, 042701] Published Thu Apr 02, 2020

The jellium model of free electron gas and its extended version have been widely used to understand the neutralization of alkali-metal ions on metal surfaces. We report an unexpected deviation from its prediction that we observed in the neutralization of $\mathrm{N}{\mathrm{a}}^{+}$ ions scattering from an Al(111) surface. …

[Phys. Rev. A 101, 032706] Published Thu Mar 26, 2020

We report on experimental elastic differential and integral cross sections for electron scattering from bismuth. The energy range of those measurements is 10–100 eV, while the scattered electron angular range in the differential cross section data is ${10}^{\circ }–{150}^{\circ }$. We also supplement our experimental res…

[Phys. Rev. A 101, 032704] Published Mon Mar 23, 2020

We study the van der Waals interaction between Rydberg alkali-metal atoms with fine structure ($n^2{L}_j$; $L\le 2$) and heteronuclear alkali-metal dimers in the ground rovibrational state ($X{}^1\mathrm{\Sigma }^{+}$; $v=0, J=0$). We compute the associated $C_6$ dispersion coefficients of atom-molecule pairs involving ${}^{133}\mathrm{Cs}$ and ${}^{85}\mathrm{Rb}$ ato…

[Phys. Rev. A 101, 032705] Published Mon Mar 23, 2020

The long-range interactions among two- or three-atom systems are of considerable importance in the cold and ultracold research areas for many-body systems. For an ion and an atom, the long-range interaction potential is dominated by the induction (or polarization) potential resulting from the (class…

[Phys. Rev. A 101, 032702] Published Mon Mar 16, 2020

Measurements of interactions between cold molecules and ultracold atoms can allow for a detailed understanding of fundamental collision processes. These measurements can be done using various experimental geometries, including where both species are in a beam, where one species is trapped, or when b…

[Phys. Rev. A 101, 032703] Published Mon Mar 16, 2020

We employ an ab initio theory to address several inconsistencies of the empirical scaling of photo-double-ionization (PDI) to electron impact ionization suggested by Samson [Phys. Rev. Lett. 65, 2861 (1990)]. We do so (i) by isolating the only relevant dipole component of the electron impact ionizat…

[Phys. Rev. A 101, 032701] Published Mon Mar 09, 2020

For ${\mathrm{U}}^{89+}$ projectiles colliding at a beam energy of 75.91 MeV/u with a ${\mathrm{N}}_2$ target, we present a coincidence measurement between the cusp electrons emitted under an angle of $0^{\circ }$ with respect to the projectile beam and the photons emitted under a polar angle of ${90}^{\circ }$. This radiative-electron-capture-to-con…

[Phys. Rev. A 101, 022708] Published Fri Feb 28, 2020

The orbital Feshbach resonance (OFR) is a recently developed scheme for magnetically tuning the interactions in closed-shell fermionic atoms. Remarkably, unlike the Feshbach resonances in alkali-metal atoms, the open and closed channels of the OFR are only very weakly detuned in energy. This leads t…

[Phys. Rev. A 101, 022707] Published Thu Feb 20, 2020

Chemical reaction dynamics is known to be influenced by quasibound states (unstable electron standing waves) that exist in the positive-energy continuum in the spatial neighborhood of molecules. These unstable spatial structures give rise to resonances in the scattering dynamics between molecules or…

[Phys. Rev. A 101, 022706] Published Tue Feb 18, 2020

Violation of centrosymmetry (VOC) in time-resolved diffraction patterns has been predicted in ultrafast-electron and x-ray diffraction from electronic and molecular motions. Extending from our x-ray studies, we theoretically investigate the VOC in time-resolved ultrafast-electron diffraction from ro…

[Phys. Rev. A 101, 022704] Published Fri Feb 14, 2020

The trapped ${}^{171}\mathrm{Yb}^{+}$ ion is a promising candidate for portable atomic clock applications. However, with buffer-gas cooled ytterbium ions, the ions can be pumped into a low-lying ${}^{2}F_{7/2}$ state or form ${\mathrm{YbH}}^{+}$ molecules. These dark states reduce the fluorescence signal from the ions and can degrade the clock…

[Phys. Rev. A 101, 022705] Published Fri Feb 14, 2020

Electron-impact excitation and ionization of H-like ions of nuclear charge $Z=2,\cdots ,8$ have been calculated from thresholds to high energies, with a particular focus on spin asymmetry of the cross sections. It is found that the importance of electron exchange is undiminished with increasing $Z$. Away from…

[Phys. Rev. A 101, 022703] Published Mon Feb 10, 2020

The inner-shell electron-impact excitation from the ground state to the $1s2s^{2}2p_{1/2}{J}_f=1$ excited state and the subsequent electric-dipole $1s2s^{2}2p_{1/2}{J}_f=1\to 1s^{2}2s^2{J}_i=0$ radiative decay of berylliumlike ions with zero nuclear spin have been studied within the framework of the multiconfigurational Dirac-Fock…

[Phys. Rev. A 101, 022701] Published Mon Feb 03, 2020

A model-potential method is employed to calculate binding, elastic scattering, and annihilation of positrons for a number of atoms and small nonpolar molecules, namely, Be, Mg, He, Ar, ${\mathrm{H}}_2, {\mathrm{N}}_2, {\mathrm{Cl}}_2$, and ${\mathrm{CH}}_4$. The model potential contains one free parameter for each type of atom within the target. Its …

[Phys. Rev. A 101, 022702] Published Mon Feb 03, 2020

The energy-dependent frame transformation theory of Gao and Greene [H. Gao and C. H. Greene, Phys. Rev. A 42, 6946 (1990)] is extended to yield a quantitatively accurate description of the dissociative recombination process. Evidence is presented to show that direct application of the original theor…

[Phys. Rev. A 101, 012709] Published Tue Jan 28, 2020

We introduce a combined molecular-dynamics and quantum-trajectories code to simulate the effects of near-resonant optical fields on state-vector evolution and particle motion in a collisional system. In contrast to collisionless systems, in which the quantum dynamics of multilevel, laser-driven part…

[Phys. Rev. A 101, 012710] Published Mon Jan 27, 2020

Coulomb-explosion imaging is a broadly employed technique to reconstruct the geometry of molecules from the direct multibody breakups of its ions. However, we reveal that this technique fails for a large class of systems, such as (${\mathrm{CO})}_2{}^{3+}$ and ${\mathrm{ArCO}}^{3+}$, since the events of the “direct breakup channel” a…

[Phys. Rev. A 101, 012707] Published Tue Jan 21, 2020

We present a fully relativistic calculation of the bremsstrahlung emitted by twisted electrons propagating in the field of bare heavy nuclei. The electron-nucleus interaction is accounted for to all orders in the nuclear binding strength parameter $\alpha Z$, thus allowing us to investigate the bremsstrahlu…

[Phys. Rev. A 101, 012708] Published Tue Jan 21, 2020

Atomic clocks based on an ${\mathrm{Al}}^{+}$ ion sympathetically cooled by a laser-cooled alkaline-earth-metal ion have achieved unprecedented accuracy. Here, we investigate theoretically interactions and charge-transfer dynamics of an ${\mathrm{Al}}^{+}$ ion immersed in an ultracold gas of Rb and Sr atoms. We calculate potential…

[Phys. Rev. A 101, 012705] Published Thu Jan 16, 2020

We present a theoretical study of rotationally elastic and inelastic collisions between molecular nitrogen ions and Rb atoms in the sub-Kelvin temperature regime prevalent in ion-atom hybrid trapping experiments. The cross sections for rotational excitation and de-excitation collisions were calculat…

[Phys. Rev. A 101, 012706] Published Thu Jan 16, 2020

The dynamics of charge-state fractions of relativistic gold-ion beams stripped by foils from Be to Au is investigated in the 100 MeV/u to 10 GeV/u energy range. Calculations of the fractions as a function of foil thickness are performed using the recently developed breit code based on the analytical…

[Phys. Rev. A 101, 012704] Published Mon Jan 13, 2020

Interspecies interaction strength between ${}^7$Li and ${}^{87}$Rb atoms through cross-dimensional relaxation of two-element gas mixtures is measured experimentally and calculated with Monte Carlo simulations. A disagreement between those two results provides an interesting challenge for interpretation and may stimulate further work.

[Phys. Rev. A 101, 012703] Published Fri Jan 10, 2020

We have computed the thermally averaged total, elastic rate coefficient for the collision of a room-temperature helium atom with an ultracold lithium atom. This rate coefficient has been computed as part of the characterization of a cold-atom vacuum sensor based on laser-cooled ${}^6\mathrm{Li}$ or ${}^7\mathrm{Li}$ atoms that…

[Phys. Rev. A 101, 012702] Published Mon Jan 06, 2020

We report measurements of shifts in the frequencies of $1{}^{3}S_1\to 2{}^{3}P_J$ and $2{}^{3}P_J\to n{}^{3}D/n{}^{3}S$ transitions optically driven in positronium atoms while they are inside the open volumes of MgO smoke powder. The observed intervals are larger than the corresponding vacuum excitations, but, surprisingly, the transiti…

[Phys. Rev. A 101, 012701] Published Thu Jan 02, 2020

We derive a pseudopotential in two dimensions (2D) with a 2D Rashba spin-orbit coupling (SOC), following in the same spirit of the frame transformation by Guan and Blume [Q. Guan and D. Blume, Phys. Rev. A 95, 020702(R) (2017)]. The frame transformation correctly describes the nontrivial phase accum…

[Phys. Rev. A 100, 062713] Published Fri Dec 27, 2019

Based on the recently developed interaction renormalization for the one-dimensional $p$-wave interaction, we study the problem of a single impurity immersed in a highly polarized Fermi sea. They interact through a narrow $p$-wave Feshbach resonance, so the effective range $r_0$ naturally appears in the sys…

[Phys. Rev. A 100, 062712] Published Thu Dec 26, 2019

A theoretical approach for the electron-impact vibronic excitation of molecular ions with low-lying excited electronic states is described. In this approach, the fixed-nuclear $R$-matrix method is employed to compute electron-ion scattering matrices in the Born-Oppenheimer approximation. A vibronic fr…

[Phys. Rev. A 100, 062711] Published Tue Dec 24, 2019

Inelastic processes in low-energy ${\mathrm{Ca}}^{+}+\mathrm{H}$ and ${\mathrm{Ca}}^{2+}+{\mathrm{H}}^{-}$ collisions accounting for the fine structure of calcium ions are investigated. The present study is based on ab initio nonrelativistic potentials and on modification of the potentials by switching the representation from the $LS$ to the $JJ$ coupling s…

[Phys. Rev. A 100, 062710] Published Fri Dec 20, 2019

Experimental determinations of the absolute differential positronium-formation cross sections near $0^{\circ }$ for Ne, Ar, Kr, and Xe are presented and compared with theory. The degree of forward collimation, expressed by the ratios of the differential-to-integral positronium-formation cross sections, is als…

[Phys. Rev. A 100, 062709] Published Thu Dec 19, 2019

Fully differential cross sections for single ionization of helium by fast proton impact in different kinematical regimes in the scattering plane were recently measured in a high-precision experiment [O. Chuluunbaatar et al., Phys. Rev. A 99, 062711 (2019)] and calculated using the first Born approxi…

[Phys. Rev. A 100, 062708] Published Wed Dec 18, 2019

We report experimental investigations of two-body fragmentation of ${\mathrm{C}}_2{{\mathrm{H}}_2}^{2+}$ induced by 1 keV electron collision utilizing an ion momentum imaging spectrometer. With the ion-ion coincidence measurement, dissociation channels ${\mathrm{C}}_2{{\mathrm{H}}_2}^{2+}\to {\mathrm{H}}^{+}+{\mathrm{C}}_2{\mathrm{H}}^{+}$ (deprotonation) and ${\mathrm{C}}_2{{\mathrm{H}}_2}^{2+}\to {{\mathrm{H}}_2}^{+}+{{\mathrm{C}}_2}^{+}$ (${{\mathrm{H}}_2}^{+}$ formation) are directly…

[Phys. Rev. A 100, 062707] Published Mon Dec 16, 2019

Cross sections for positron scattering from molecular nitrogen are reported for energies below the positronium formation threshold. The elastic and state-to-state rotational and vibrational cross sections were obtained within the close-coupling formalism, using a three-dimensional potential energy s…

[Phys. Rev. A 100, 062706] Published Wed Dec 11, 2019

The alignment parameter $A_{20}$ of ${}_{73}\mathrm{Ta}, {}_{74}\mathrm{W}$, and ${}_{79}\mathrm{Au}$ ions after $L_3$ subshell ionization by electron impact has been determined experimentally and theoretically in the wide energy range $(1.02–10.2)E_{L_3}$, where $E_{L_3}$ is the $L_3$ ionization threshold. The $A_{20}$ values have been deduced from measurements of the $L\ell$…

[Phys. Rev. A 100, 062705] Published Tue Dec 10, 2019

We study the atom-exchange reaction involving Feshbach molecules in the overlapping Feshbach resonance at about 106.8 G in the ${}^{23}\mathrm{Na}{}^{40}\mathrm{K}$ system. We measure the reaction-rate coefficients as a function of the magnetic field in the exothermic regime. The measured reaction-rate coefficients in the curren…

[Phys. Rev. A 100, 062704] Published Fri Dec 06, 2019

We study the effect of crystal lattice vibrations on grazing-incidence fast atom diffraction (GIFAD) from insulator surfaces. To describe the phonon contribution to GIFAD we introduce a semiquantum method named phonon-surface initial value representation (P-SIVR), which represents the surface with a…

[Phys. Rev. A 100, 062703] Published Thu Dec 05, 2019

In the present work we study the applicability of the binary-encounter-dipole (BED) model and its simpler version the binary-encounter-Bethe model for positron-impact direct ionization. We show that ignoring the exchange and interference effects in the theory of Kim and Rudd [Phys. Rev. A 50, 3954 (…

[Phys. Rev. A 100, 062702] Published Wed Dec 04, 2019

Electron-impact single-ionization cross sections for the ${\mathrm{W}}^{5+}$ ion have been studied experimentally and theoretically. Measurements of a detailed ionization spectrum and of absolute cross sections were performed employing the crossed-beams method in the energy range from the ionization onset up to 100…

[Phys. Rev. A 100, 062701] Published Tue Dec 03, 2019

We consider binary-encounter electron emission in relativistic ion-atom collisions in the presence of a monochromatic low-frequency plane-wave electromagnetic field of circular polarization. The parameters of the field—its intensity and frequency—are chosen in such a way that the field per se has a …

[Phys. Rev. A 100, 052710] Published Wed Nov 27, 2019

We present experimental and theoretical cross sections for elastic electron scattering from ${\mathrm{CHCl}}_3$. This is an important target because of its relevance to environmental chemistry and the plasma etching industry as a source of chlorine radicals. The experimental results were obtained at incident elec…

[Phys. Rev. A 100, 052709] Published Tue Nov 26, 2019

The double electron loss (DEL) from ${\mathrm{He}}^{-}$ has been investigated in collisions with He atoms at 300-keV impact energy and at electron energies that satisfy the cusp condition; i.e., the corresponding electron velocities match the projectile's velocity. In a time-of-flight experiment the energies of bot…

[Phys. Rev. A 100, 052708] Published Mon Nov 25, 2019

The elastic scattering properties of three bosons at low energy enter the many-body description of ultracold Bose gases via the three-body scattering hypervolume $D$. We study this quantity for identical bosons that interact via a pairwise finite-range potential. Our calculations cover the regime from…

[Phys. Rev. A 100, 050702(R)] Published Thu Nov 21, 2019

We calculated the nonlinear screening and the electronic stopping of energetic helium ions in a III-V compound semiconductor at low speeds below stopping maximum under channeling conditions. For the range of velocity considered, it is found the energy loss of the intruding ions show pronounced depen…

[Phys. Rev. A 100, 052707] Published Wed Nov 20, 2019

Formation mechanism of ${\mathrm{H}}_3^{+}$ ions from doubly charged hydrocarbons ($\mathrm{C}{\mathrm{H}}_4$ and ${\mathrm{C}}_2{\mathrm{H}}_4$) is investigated by combining charged particle (300 eV electrons and 3 keV/u ${\mathrm{Ar}}^{8+}$ ions) collision experiments and quantum chemistry calculations. The kinetic energy release (KER) distribution for each ${\mathrm{H}}_3^{+}$ loss process was…

[Phys. Rev. A 100, 052706] Published Tue Nov 19, 2019

Single ionization by electron impact of the ${\mathrm{Fe}}^{3+}$ ion is investigated using the Dirac-Fock-Slater approximation for the levels of the ground and first-excited $3d^{4}4s$ configuration. Contributions from direct ionization (DI) and excitation-autoionization (EA) processes are taken into account. The scaled…

[Phys. Rev. A 100, 052705] Published Mon Nov 18, 2019

We investigate the use of microwave radiation to produce a repulsive shield between pairs of ultracold polar molecules and prevent collisional losses that occur when molecular pairs reach short range. We carry out coupled-channels calculations on $\mathrm{RbCs}+\mathrm{RbCs}$ and $\mathrm{CaF}+\mathrm{CaF}$ collisions in microwave fields.…

[Phys. Rev. A 100, 052704] Published Thu Nov 14, 2019

The three-body parameter (3BP) $a_{-}^{\left(1\right)}$ is crucial for understanding Efimov physics, and a universal 3BP has been shown in experiments and theory in ultracold homonuclear gases. The 3BP of heteronuclear systems has been predicted to possess much richer properties than its homonuclear counterparts due t…

[Phys. Rev. A 100, 052702] Published Tue Nov 12, 2019

We propose a type of Feshbach resonance occurring when two different ultracold atoms in their ground state undergo an $s$-wave collision in the presence of a laser. The collisional levels of the atom pair are coupled by the laser to a rovibrational molecular level of the same electronic ground state: …

[Phys. Rev. A 100, 052703] Published Tue Nov 12, 2019

We report on the observation of dipolar splitting in ${}^6\mathrm{Li}p$-wave Feshbach resonances by high-resolution atom-loss spectroscopy. The Feshbach resonances at 159, 185, and $215\mathrm{G}$ exhibit a doublet structure of 10, 6, and $13\mathrm{mG}$, respectively, associated with different projections of the orbital angular momen…

[Phys. Rev. A 100, 050701(R)] Published Mon Nov 11, 2019

Selective bond breaking in a molecule with the use of photons opens the way to control chemical reactions. We demonstrate here that dissociation of a molecule can be efficiently achieved by first photoexciting a neighboring atom or molecule. On the example of the giant $\mathrm{He}-{\mathrm{H}}_2$ dimer, we show that simu…

[Phys. Rev. A 100, 052701] Published Mon Nov 11, 2019

Doubly polar molecules, possessing an electric dipole moment and a magnetic dipole moment, can strongly couple to both an external electric field and a magnetic field, providing unique opportunities to exert full control of the system quantum state at ultracold temperatures. We propose a method for …

[Phys. Rev. A 100, 042711] Published Tue Oct 29, 2019

We revisit the basic properties of Fano-Feshbach resonances in two-body systems with van der Waals tail interactions, such as ultracold neutral atoms. Using a two-channel model and two different methods, we investigate the relationship between the width and shift of the resonances and their dependen…

[Phys. Rev. A 100, 042710] Published Mon Oct 28, 2019

The feasibility of producing the molecular antihydrogen anion ${{\overline{\mathrm{H}}}_2}^{-}$ in the laboratory is investigated. Utilizing reaction rates calculated here involving the interaction of laser excited-state antihydrogen atoms held in magnetic minimum traps, key processes are identified that could lead to anion pro…

[Phys. Rev. A 100, 042709] Published Thu Oct 24, 2019

It was shown recently that the discrete scaling symmetry, which underlies the Efimov effect in the three identical boson system with two-body short-range interactions, survives when single-particle one-dimensional (1D) spin-orbit coupling terms are added to the Hamiltonian. Each three-body energy le…

[Phys. Rev. A 100, 042708] Published Mon Oct 21, 2019

We report the observation of a dimer-dimer inelastic collision resonance for ultracold Feshbach molecules made of bosonic sodium and rubidium atoms. This resonance, which we attribute to the crossing of the dimer-dimer threshold with a heteronuclear tetramer state, manifests itself as a pronounced i…

[Phys. Rev. A 100, 042706] Published Mon Oct 14, 2019

We calculate the effective three-body force for bosons interacting with each other by a two-body potential tuned to a narrow zero crossing in any dimension. We use the standard two-channel model parametrized by the background atom-atom interaction strength, the amplitude of the open-channel to close…

[Phys. Rev. A 100, 042707] Published Mon Oct 14, 2019

In this paper two theoretical methodologies, the Schwinger multichannel (SMC) method and the independent atom model with the screening corrected additivity rule (IAM-SCAR), were employed to study positron scattering by benzene over a broad impact energy range. The SMC calculations were carried out i…

[Phys. Rev. A 100, 042705] Published Wed Oct 09, 2019

The convergent close-coupling method has been applied to positron scattering by the hydrogen negative ion. Convergence of the cross sections is achieved and internal consistency of the method is verified using both the single- and two-center approaches. Calculations were performed using accurate tar…

[Phys. Rev. A 100, 042703] Published Tue Oct 08, 2019

In the current work, we investigate the ionization of water molecules impacted by neutral hydrogen and proton beams. The continuum distorted wave-eikonal initial-state approximation is used to describe the reaction. Differential and total cross sections are compared with the available experimental d…

[Phys. Rev. A 100, 042704] Published Tue Oct 08, 2019

We analyze the quantum mechanics of the friction experienced by a small system as it moves nondestructively with velocity $v$ over a surface. Specifically, we model the interactions between the system and the surface with a collision model. We show that under weak assumptions, the magnitude of the fri…

[Phys. Rev. A 100, 042702] Published Wed Oct 02, 2019

We previously predicted [P. A. Hervieux et al., Phys. Rev. A 95, 020701(R) (2017)] that, owing to predominant electron capture by incoming positrons from the molecular shell, ${\mathrm{C}}_{60}$ acts like a spherical diffractor inducing resonances in the positronium (Ps) formation as a function of the positron imp…

[Phys. Rev. A 100, 042701] Published Tue Oct 01, 2019

Anion and cation emission following water dissociation was studied for 6.6-keV ${}^{16}{\mathrm{O}}^{+}+{\mathrm{H}}_2\mathrm{O}$ collisions. Absolute cross sections for the emission of all positively and negatively charged fragments, differential in both energy and observation angle, were measured. The fragments formed in hard, binary coll…

[Phys. Rev. A 100, 032713] Published Fri Sep 27, 2019

This work addresses the modeling of the resonant neutralization of positive alkali-metal ions near metal surfaces. Usually the charge, induced by a positive ion, is taken into account by means of point image charge, located symmetrically to the image plane. Such an approach describes the ion level s…

[Phys. Rev. A 100, 032712] Published Tue Sep 24, 2019

The approach suggested previously to treat the mean energy loss of charged projectiles in terms of induced currents is extended to describe the energy-loss straggling. It has been shown that, provided the perturbed wave function of electrons is known, the phenomenon can be represented in a form of d…

[Phys. Rev. A 100, 032711] Published Mon Sep 23, 2019

A recent experimental study of the energy losses of various ions in titanium nitride, in the low-energy range [M. A. Sortica et al., Sci. Rep. 9, 176 (2019)], showed a striking departure of the measured values from those predicted by density functional theory. They suggested electron promotion in a…

[Phys. Rev. A 100, 030701(R)] Published Fri Sep 20, 2019

We report an electron momentum spectroscopy study on valence shake-up satellites of neon. A symmetric noncoplanar $(e,2e)$ experiment was performed at an incident electron energy of 1.2 keV, and the recoil-ion-momentum–dependent $(e,2e)$ cross sections or momentum profiles of the shake-up satellites hav…

[Phys. Rev. A 100, 032710] Published Fri Sep 20, 2019

A simple analytical formula for partial wave cross section describing low-energy elastic scattering in the presence of a shape resonance located near the elastic threshold is proposed. The formula is based on the extension of the regularized method of analytical continuation in the coupling constant…

[Phys. Rev. A 100, 032709] Published Thu Sep 19, 2019

We derive a quasiclassical expression for the density of states (DOS) of an arbitrary, ultracold, $N$-atom collision complex, for a general potential energy surface (PES). We establish the accuracy of our quasiclassical method by comparing to exact quantum results for the ${\mathrm{K}}_2\text{−}\mathrm{Rb}$ and NaK-NaK systems, wi…

[Phys. Rev. A 100, 032708] Published Tue Sep 17, 2019

We report on the investigation of endothermic and nearly thermoneutral atom-exchange collisions in an ultracold atom-dimer mixture. By developing an indirect preparation method based on a molecular bound-bound transition, we are able to directly observe an endothermic collision with a tunable energy…

[Phys. Rev. A 100, 032706] Published Mon Sep 16, 2019

We have measured and calculated fully differential cross sections (FDCS) for ionization of helium by 75-keV proton impact. Ejected electrons with a speed close to and above the projectile speed were investigated. This range of kinematics represents a largely unexplored regime. A high sensitivity of …

[Phys. Rev. A 100, 032707] Published Mon Sep 16, 2019

Electronic stopping cross sections (SCSs) of nickel, silicon, and nickel-silicon alloys for protons and helium (He) ions are studied in the regime of medium- and low-energy ion scattering, i.e., for ion energies in the range from $500\mathrm{eV}$ to $200\mathrm{keV}$. For protons, at velocities below the Bohr velocity th…

[Phys. Rev. A 100, 032705] Published Wed Sep 11, 2019

We present interferometeric measurements of the $f=1$ to $f=2$ interhyperfine scattering lengths in a single-domain spinor Bose-Einstein condensate of ${}^{87}\mathrm{Rb}$. The interhyperfine interaction leads to a strong and state-dependent modification of the spin-mixing dynamics with respect to a noninteracting desc…

[Phys. Rev. A 100, 032704] Published Tue Sep 10, 2019