Effective range theory, taking into account the polarisation interaction, is used for the extrapolation of the phaseshifts for the scattering of electrons by heavy alkali atoms to the region of thermal energies. The phaseshifts obtained are used for the calculation of impact broadening and the shift of Rydberg levels by alkali perturbers in the ground state. The parameters of the theory obtained from the ab initio calculations give a good description of the data on broadening and shift in the case of K and Rb. In the case of Cs the parameters have to be somewhat modified to give an agreement with experiment. The phaseshifts are also used for the calculation of the width and shift in the free-electron spin-resonance frequency due to collisions with heavy alkali atoms. The results of calculations are in good agreement with experimental data. The results for total and momentum transfer cross sections for the scattering of electrons with energies from 10 -4 to 10 -1 eV by K, Rb and Cs atoms are presented.Effective range theory, taking into account the polarisation interaction, is used for the extrapolation of the phaseshifts for the scattering of electrons by heavy alkali atoms to the region of thermal energies. The phaseshifts obtained are used for the calculation of impact broadening and the shift of Rydberg levels by alkali perturbers in the ground state. The parameters of the theory obtained from the ab initio calculations give a good description of the data on broadening and shift in the case of K and Rb. In the case of Cs the parameters have to be somewhat modified to give an agreement with experiment. The phaseshifts are also used for the calculation of the width and shift in the free-electron spin-resonance frequency due to collisions with heavy alkali atoms. The results of calculations are in good agreement with experimental data. The results for total and momentum transfer cross sections for the scattering of electrons with energies from 10 -4 to 10 -1 eV by K, Rb and Cs atoms are presented.

Journal of Physics B Atomic and Molecular PhysicsMay 28, 198682 citations

Negative-ion resonances in cross sections for slow-electron–heavy-alkali-metal-atom scattering

Cristian Bahrim, Uwe Thumm, I. I. Fabrikant

We analyze negative-ion resonances in elastic and inelastic total scattering cross sections for slow electron collisions with the heavy-alkali-metal atoms Rb, Cs, and Fr. Our calculations are based on the Dirac $R$ -matrix method [Thumm and Norcross, Phys. Rev. A 45, 6349 (1992)]. For incident electrons of up to 2.8 eV kinetic energy, we compare a ${}^{3}{P}^{o}$ shape resonance and ${}^{3}{P}^{e},$ ${}^{1}{P}_{1}^{o},$ and ${}^{1}{D}_{2}^{o}$ Feshbach resonances, located below the first excitation threshold of the atomic target in the low-lying spectra of the ${\mathrm{Rb}}^{\ensuremath{-}},$ ${\mathrm{Cs}}^{\ensuremath{-}},$ and ${\mathrm{Fr}}^{\ensuremath{-}}$ negative ions, with available experimental data and other calculations. We provide the resonance parameters, partial and converged total elastic and inelastic scattering cross sections, and discuss the relative importance of relativistic effects for the three heavy-alkali-metal targets.We analyze negative-ion resonances in elastic and inelastic total scattering cross sections for slow electron collisions with the heavy-alkali-metal atoms Rb, Cs, and Fr. Our calculations are based on the Dirac $R$-matrix method [Thumm and Norcross, Phys. Rev. A 45, 6349 (1992)]. For incident electrons of up to 2.8 eV kinetic energy, we compare a ${}^{3}{P}^{o}$ shape resonance and ${}^{3}{P}^{e},$ ${}^{1}{P}_{1}^{o},$ and ${}^{1}{D}_{2}^{o}$ Feshbach resonances, located below the first excitation threshold of the atomic target in the low-lying spectra of the ${\mathrm{Rb}}^{\ensuremath{-}},$ ${\mathrm{Cs}}^{\ensuremath{-}},$ and ${\mathrm{Fr}}^{\ensuremath{-}}$ negative ions, with available experimental data and other calculations. We provide the resonance parameters, partial and converged total elastic and inelastic scattering cross sections, and discuss the relative importance of relativistic effects for the three heavy-alkali-metal targets.

Physical Review AMar 19, 200136 citations

Electron-Atom Resonances

Frank H. Read

Kluwer Academic Publishers eBooksDec 15, 20050 citations

Fano profiles of Efimov resonances in mass-imbalanced ultracold gases

Panagiotis Giannakeas, Chris H. Greene

The resonant profile of the rate coefficient for three-body recombination into a shallow dimer is investigated for mass-imbalanced systems. In the low-energy limit, three atoms collide with zero-range interactions, in a regime where the scattering lengths of the heavy-heavy and the heavy-light subsystems are positive and negative, respectively. For this physical system, the adiabatic hyperspherical representation is combined with a fully semi-classical method and we show that the shallow dimer recombination spectra display an asymmetric Fano lineshape that originates from the coexistence of Efimov resonances with Stuckelberg interference minima. In particular, a closed form expression is derived that describes the width of the corresponding Efimov resonances and the Fano lineshape asymmetry parameter $q$ . The profile of Efimov resonances exhibits a $q-$ reversal effect as the inter- and intra-species scattering lengths vary. In the case of a diverging asymmetry parameter, i.e. $|q|\to \infty$ , we show that the Efimov resonances possess zero width and are fully decoupled from the three-body and atom-dimer continua, and the corresponding Efimov metastable states behave as bound levels.The resonant profile of the rate coefficient for three-body recombination into a shallow dimer is investigated for mass-imbalanced systems. In the low-energy limit, three atoms collide with zero-range interactions, in a regime where the scattering lengths of the heavy-heavy and the heavy-light subsystems are positive and negative, respectively. For this physical system, the adiabatic hyperspherical representation is combined with a fully semi-classical method and we show that the shallow dimer recombination spectra display an asymmetric Fano lineshape that originates from the coexistence of Efimov resonances with Stuckelberg interference minima. In particular, a closed form expression is derived that describes the width of the corresponding Efimov resonances and the Fano lineshape asymmetry parameter $q$. The profile of Efimov resonances exhibits a $q-$reversal effect as the inter- and intra-species scattering lengths vary. In the case of a diverging asymmetry parameter, i.e. $|q|\to \infty$, we show that the Efimov resonances possess zero width and are fully decoupled from the three-body and atom-dimer continua, and the corresponding Efimov metastable states behave as bound levels.

Sep 28, 20210 citations

Resonances in the scattering of atoms and molecules

J. P. Toennies

Jan 1, 19800 citations

R

-matrix method [Thumm and Norcross, Phys. Rev. A 45, 6349 (1992)]. For incident electrons of up to 2.8 eV kinetic energy, we compare a

{}^{3}{P}^{o}

shape resonance and

{}^{3}{P}^{e},

{}^{1}{P}_{1}^{o},

and

{}^{1}{D}_{2}^{o}

Feshbach resonances, located below the first excitation threshold of the atomic target in the low-lying spectra of the ${\mathrm{Rb}}^{\ensuremath{-}},$ ${\mathrm{Cs}}^{\ensuremath{-}},$ and ${\mathrm{Fr}}^{\ensuremath{-}}$ negative ions, with available experimental data and other calculations. We provide the resonance parameters, partial and converged total elastic and inelastic scattering cross sections, and discuss the relative importance of relativistic effects for the three heavy-alkali-metal targets.

q

. The profile of Efimov resonances exhibits a

q-

reversal effect as the inter- and intra-species scattering lengths vary. In the case of a diverging asymmetry parameter, i.e.

|q|\to \infty

, we show that the Efimov resonances possess zero width and are fully decoupled from the three-body and atom-dimer continua, and the corresponding Efimov metastable states behave as bound levels.