Impulse-approximation analysis of collisions between Rydberg and ground-state rubidium atoms at thermal energies

Abstract

The impulse approximation for the Rydberg atom-atom collisions is analyzed on the basis of the Faddeev equations. A modified expression is derived for the cross sections, including the interference between the Rydberg-electronperturber scattering and the ion-coreperturber scattering. This expression is used for the calculations of the collisional quenching and elastic scattering in Rb( nS)-Rb and Rb( nP)-Rb collisions. We use the electron-Rb scattering phase shifts obtained from ab initio close-coupling calculations and their extrapolation, applying the modified effective-range theory. Our results show that the impulse approximation agrees with the experimental data for the quenching cross sections at n )20 but underestimates the quenching cross sections at lower n. The position of the maximum of the cross section is in good agreement with experimental data. We also obtain reasonable results for the elastic cross section at n )20, but for the lower n the results are too large. The interference effect plays a minor role in the process, which means that simultaneous electron-perturber and ion-perturber interaction is unlikely.PACS number(s): 34.60.+ z, 32.70.Jz

Similarity between Positronium-Atom and Electron-Atom Scattering

“…The amplitudes f ± in Eq. (1) are off the energy shell in the sense that [2,15]. In order to employ the physical scattering amplitude, we perform the on-shell reduction following Starrett et al [14] and assume that each amplitude is a function of the effective velocity v ± = max(v ± i , v ± f ) and momentum transfer s = |∆p| linked to the scattering angle θ ± by s = 2v ± sin(θ ± /2).…”

“…By contrast, large-scale numerical calculations for specific targets may be capable of reproducing experimental data but often lack the transparency required for providing physical insight. Note that the present impulse-approximation approach can also be improved by extension of the e − -A and e + -A scattering amplitudes off the energy shell and by considering higher-order approximations of the Faddeev theory [15,27].…”

Collisional broadening of Rydberg atoms perturbed by ground-state sodium atoms

“…Calculations [3][4][5] performed in the impulse approximation have explained the general features of these processes and the large values of the broadening cross sections. However, some attempts [6] to explain the oscillatory dependence of the width on the principal quantum number in the framework of the impulse approximation failed [3].…”

Formation of positron-atom bound states in collisions between Rydberg Ps and neutral atoms

“…This allows one to use the impulse approximation (IA) (see, e.g., Refs. [94,[98][99][100][101]) and write the corresponding amplitude in the form…”