Double-electron capture

He(ls ) S and also from the metastable level Nr (ls2s)-1- He(ls ) in order to take care of the fraction of metastable ion in the incident beam, as well as the double-electron capture process from both ground and metastable ions. 

DOUBLE-ELECTRON CAPTURE PROCESS FROM THE GROUND STATE n5+(1s2)1S + He(ls2)iS... 

Assuming the contribution of the potential energy curves which have not been taken into account to be almost constant with the collision energy, such calculations could provide a relative estimate of the variation of the double capture cross-sections with the collision energy. The results presented in Fig. 7 seem to be coherent with this hypothesis and to corroborate a cascade effect for the double electron capture process. 

SINGLE AND DOUBLE ELECTRON CAPTURE IN BORON COLLISION SYSTEMS... 

B4++ He reaction. This collisional system has been investigated theoretically within the framework of the semiclassical close-coupling formalism using different model potential approaches [2,3] which lead to a discrepancy of about a factor 5 for the double capture cross section values. We have thus performed an alternative study of this system by means of a full molecular expansion method, focusing our attention on the double electron capture process. 

TABLE 2. Comparison of asymptotic energy values with experimental [13] (single-electron capture levels) and theoretical data [17] (double-electron capture levels) (ina.u)... 

This work provides accurate potential energy curves as well as coupling matrix elements for the B2+/H and B4+/ He systems. From the molecular point of view, it appears important to involve all levels correlated to the entry channels in the collision dynamics and, in particular, to take into account rotational effects, which might be quite important. The results concerning the double electron capture process in the (B4+ + He) collision point out the limitations ofthe potential approach model, especially to account for open shell levels, for which more elaborate calculations are necessary. 

Single and double electron capture in boron collision systems 133... 

It has otherwise been shown experimentally [5] that the double-electron capture oeeurs mainly from the N fls ) + He(ls ) ground state. We have thus neglected the eontribu-tion of the N (ls2s) metastable ion. 

The potential energy curves of the E, TI and one states involved in the single- and double-electron capture processes are displayed in Fig. 1. The n and A potential energy curves show no evidence of avoided crossings, but three avoided crossings appear in the range [6.0-9.0 a.u.] between the entry channel and the -t- He ) states of... 

McEwen, C. N. Fagan, P. J. Krusic, P. J., Mass Spectrometry of Perfluoroalkylated Buckminsterfullerene A Case for Sequential Gas Phase Double Electron Capture. Int. J. Mass Spectrom. 1995,146-147, 297-304. 

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