Atomic scattering in the diffraction limit: electron transfer in keV Li  Na(3s, 3p) collisions

Abstract

We measure angle differential cross sections (DCS) in Li+ + Na → Li + Na+ electron transfer collisions in the 2.7–24 keV energy range. We do this with a newly constructed apparatus which combines the experimental technique of cold target recoil ion momentum spectroscopy with a laser-cooled target. This setup yields a momentum resolution of 0.12 au, an order of magnitude better angular resolution than previous measurements on this system. This enables us to clearly resolve Fraunhofer-type diffraction patterns in the angle DCS. In particular, the angular width of the ring structure is given by the ratio of the de Broglie wavelength λdB = 150 fm at a velocity v = 0.20 au and the effective atomic diameter for electron capture 2R = 20 au. Parallel AO and MO semiclassical coupled-channel calculations of the Na(3s, 3p) → Li(2s, 2p) state-to-state collision amplitudes have been performed, and quantum scattering amplitudes are derived by the eikonal method. The resulting angle-differential electron transfer cross sections and their diffraction patterns agree with the experimental level-to-level results over most scattering angles in the energy range.

Atomic-matter-wave diffraction evidenced in low-energy Na++Rb charge-exchange collisions

“…However, this basis set is not complete enough to yield an accurate description of the χ k molecular states, mainly because of the lack of underlying orbitals sharply peaked on the nuclear centers, which are necessary to describe the effect of the ionic cores on the χ k orbitals. Following [28,29], we accordingly complete the OEDM set by Gaussian-type orbital (GTO) basis sets on both nuclei G (n 1 ,n 2 ) k (r Na,Rb ) = N (n 1 ,n 2 ) k x n 1 Na,Rb z n 2 Na,Rb e −α k r 2 Na,Rb , (10) where x Na,Rb and z Na,Rb are the Cartesian coordinates of the electronic vectors r Na and r Rb defined in the molecular frame withẑ ||R and (x,ẑ) = (v,b). N (n 1 ,n 2 ) k is a normalization factor, while n 1 and n 2 are integers such that 0 n 1 + n 2 2.…”

“…The resulting MOTRIMS setup indeed provides stateselective differential cross sections, with hitherto unsurpassed accuracy, due to the extremely low target cloud temperature. Many experiments have been performed worldwide [7][8][9][10][11][12][13][14][15][16], using alkali-metal atomic targets, and have revealed detailed information on single-and multielectron capture processes.…”

Theoretical study of the low-lying adiabatic states of the NaLi + molecular ion

“…From the experimental prespective, direct measurements of crossed-beam reaction rate coefficients for the production of NaLi + ions, have been reported by Johnson et al [13]. Several other experimental studies involving indirectly this molecular ion, have been motivated by the measurement of cross sections of charge transfer process which occurs in Li + /Na collisions [14,15,16,17,18]. From the theoretical point of view, besides computation of charge transfer cross sections which has motivated several studies [19,20,21,22,23], theoretical determination of the adiabatic energy curves of the NaLi + ion, has also received considerable attention.…”

Identification of distinct two-electron transfer processes in O 6+ + Na collisions

“…To calibrate the Na 2+ recoil spectra we make use of well-resolved n-states in the Na + recoil spectra [16]. The transverse momentum (p trans ) is obtained using an inverse Abel transformation [12,17,18], which is possible due to the cylindrical symmetry of the collision geometry. The Q-value spectrum is shown in fig.…”