Speaker
Description
Modelling of stellar atmospheres requires various detailed and accurate data on different processes such as the mutual neutralization (MN) of cation-anion pairs that can affect atomic species of interest. Indeed, neutralization reactions play an important role in atmospheric and astrophysical processes. Furthermore, there is a strong demand from the astrochemical community for information about the low-energy cross section of processes involving H− (or D−).
Our merged-beam setup [1] was modified in order to be able to study the mutual neutralization of 7Li++2D− ⟶ Li∗(nl)+D(1s) and determine which states of the lithium neutral atom are predominant in the total cross section. Preliminary measurements at ∼ 7 meV have been performed and compared with theoretical calculations [2]. Our apparatus gives access to the branching ratio among accessible neutral channels of the lithium atom and could discriminate the Li(3p) and Li(3d) channels separated by only 44 meV.
The measured total cross section of this study agrees with the results of Croft et al. However, our measured branching ratio suggests higher proportions of the 3d (by approximately 6%) and 3s (by approximately 5%) channels at the expense of Li(3p).
Further experiments at higher collision energies are still needed to completely compare our results with the experimental study of Pear and Hayton [3] which was restricted to higher collision energies in the range of 0.7 to 316 eV or with theoretical calculations.
References
[1] Nkambule, S. M., Elander, N., Larson, Å., Lecointre, J. and Urbain, X., Differential and total cross sections of mutual neutralization in low-energy collisions of isotopes of H++H−, Phys. Rev. A 93, 032701 (2016).
[2] Croft, H., Dickinson, A. S. and Gadéa, F. X., A theoretical study of mutual neutralization in Li+H collisions. J. Phys. B: At. Mol. Opt. Phys. 32, 81 (1999).
[3] Peart, B. and Hayton, D. A., Merged beam measurements of the mutual neutralization of He+/H− and Li+/D− ions. J. Phys. B: At. Mol. Opt. Phys. 27, 2551 (1994).
