Angular differential studies of electron transfer in collisions of He-like ions with Na(3s): The role of electron saddle crossings

Abstract

We present a systematic experimental and theoretical study of angular differential cross sections of singleelectron transfer in collisions of N 5+ , O 6+ , and Ne 8+ with ground-state Na(3s) in the collision energy range from 1 to 8 keV/amu. Experiments were performed using recoil-ion momentum spectroscopy in combination with a magneto-optically cooled Na atom target. The results are compared with three-body classical-trajectory Monte Carlo theory. Experimental and theoretical angular differential cross sections for capture into highly excited states show an oscillatory structure which is linked to the number of times the active electron crosses the potential energy saddle, i.e., oscillates between the two nuclear centers during the collision process.

Role of electron saddle swaps in the photon spectra following Li3+charge-exchange collisions with H*(n= 2), Na(3Otranto1, Hoekstra2, Olson3 2014Phys. Rev. ASelf Cite

“…In a recent joint collaboration with the Groningen group, we have studied state-selective charge-exchange processes between He-like projectiles (in particular, N 5+ and Ne 8+ ) with Na(3s) and Na * (3p). Their angular differential studies evidenced an energy-dependent oscillatory structure which was well reproduced by classical trajectory Monte Carlo (CTMC) calculations and was ascribed to the possible different numbers of electron saddle crossings which take place during the capture process [7,8]. Early on, oscillations were observed on the visible line emission cross sections for C 6+ and O 8+ collisions on Li(2s) but their origin due to electron swaps went unrecognized [9].…”

“…Since H * (n = 2) is not a feasible target for laboratory experiments, in recent years magneto-optical-trap-recoil-ion momentum-spectroscopy experiments have been conducted at KVI-Groningen using different alkali-metal targets, Li(2s), Na(3s), and Na * (3p), since their ionization potentials are * Corresponding author: sotranto@uns.edu.ar similar to H * (n = 2) [5][6][7]. It is expected that charge-exchange information on H * (n = 2), which has V ion = 3.4 eV, can be interpolated from the results obtained for Na(3s) (V ion = 5.14 eV) and Na * (3p) (V ion = 3.04 eV).…”

Role of the recoil ion in single-electron capture and single-ionization processes for collisions of protons with He and Ar atoms

“…To circumvent this issue, and provided that the transverse component that is expected to be thermally affected is that corresponding to the jet direction (y coordinate), a back-projection procedure of the p rec-x component based on the inverse Abel transform is performed to recover the cylindrical symmetry [12][13][14]. This procedure has also been implemented in MOTRIMS studies which are based in the detection of one of the transverse recoil-ion momentum components [15].…”

Oscillatory patterns in angular differential ion-atom charge exchange cross sections: The role of electron saddle swaps

“…in the longitudinal direction and about 0.2 a.u. for the transverse momentum spectra [15]. From the longitudinal component of the Na + recoil momentum, the Q-value of the collision can be deduced, and hence the product n-level.…”