Three-dimensional recoil-ion momentum analyses in 8.7 MeV O⁷⁺-He collisions

Abstract

Using high-resolution recoil-ion momentum spectroscopy we have measured the differential cross sections of single-electron capture and target single-ionization processes for 8.7 MeV 07'-He collisions as functions of scattering angle. A transverse momentum molution of hO.2 a", which componds to an angular resolution of about I I .5 x rad for the projectile scattering angle, was obtained by intersecfing a well collimated 07+ beam with a target of 3. supersonic He jet from a pre-cooled gas and by measuring the recoil-ion transverse momentum. For the single capture reaction, information on the n-value of the eleclron final state in O"(lsn1) is oblained from the longiludinal momentum of the recoil ions. In pure singleelectron capture. the dominant contributions to capture were found to be thwe from the n = 4 and higher states. whereas single capture accompanied by lhe ionization of the second target electron mainly populates n = 2 lo n = 4 states. Furthermore, the measured VansverSe momentum distribution differs significantly between pure single capture and capture with simultaneous ionization, The measured data for the pure capture process compare favourably with thenretical results based on a molecular-state expansion method. Other experimental data are discussed in terms of the classical overbarrier model.

Cold Target Recoil Ion Momentum Spectroscopy

“…The determination of the longitudinal momentum distribution alone allows for some qualitative conclusions already. Such experiments have been reported by Wu and coworkers [88] and Kambara and coworkers [133] (a). The "rst kinematical complete experiment for transfer ionization has been reported by Mergel and coworkers [68,69].…”

“…They found a maximum at around k , "1 a.u. but could not con"rm oscillations in the di!erential cross-section predicted by close coupling calculations [133].…”

“…Wu and coworkers [88] and Kambara and coworkers [133] have employed COLTRIMS to study single electron capture by 0.5}3.7 MeV/u O > and F > on He collisions. They could separate capture to the projectile K-shell from capture to higher excited states (see Fig.…”

“…At a much lower impact energy of 8.7 MeV Kambara and coworkers performed the equivalent experiment [133]. They found, that the distribution for transfer ionization is slightly backward shifted compared to the single capture distribution.…”

State-selective electron capture inHe32+Alessi1, Otranto2, Focke3 2011Phys. Rev. A

“…During the past 15 years, the incorporation of the cold-target recoil-ion momentum spectroscopy (COLTRIMS) method in several laboratories worldwide has led to an important advance in the experimental studies of atomic and molecular collisions [1][2][3][4][5][6][7][8][9]. This method allows the measurement of collision events at the fully differential level, providing, in this sense, an unprecedented kinematically complete physical picture for several collision processes.…”