Formation and stabilization of the doubly excited states in atomic collisions

H. Bachau, C. Harel, P. Roncin

The authors agree with the points raised in the comment by Vaeck and Hansen. Indeed autoionization of doubly excited Rydberg states is now included in a more complete treatment submitted for publication, a guideline of which is summarized in this reply.

R. F. Stebbings

A. P. Kazantsev

Emma J. Sokell, A A Wills, P. R. Hammond +2 more

Long-lived, excited neutral particles, arising from the interaction of monochromatic synchrotron radiation with ground state He atoms, have been observed at photon energies close to the (N = 1,2,3 and 4) ionization thresholds. The measurements have been made using an unconventional experimental arrangement in which charged particles, responsible for the dominant signal in conventional photon impact studies, are prevented from reaching the detector. For , it appears that the formation, via photoexcitation, of relatively long-lived, doubly excited Rydberg states is a necessary step in the production of the observed signal. Four processes that might account for the production of the excited neutral particles are considered. The simplest, that atoms in the initial doubly excited Rydberg states are themselves directly observable, is considered unlikely. However, the lifetimes of the photoexcited double Rydberg states may be increased through the effects of electric fields present in the apparatus. Transitions from these double Rydberg states, occurring either as a result of collisions or by fluorescence, could result in metastable, singly excited neutral particles. The presence of signal related to the existence of long-lived doubly excited states could be significant in the interpretation of other photon impact measurements.

І. І. Бондар, В. В. Суран, M. I. Dudich

Experimental investigations of resonant structure in doubly charged ion (A 2+ ) formation were carried out during Sr and Ba atom ionization by infrared laser radiation (ω = 8400-9100 cm -1 ). It has been shown that in this case the mechanism of ion formation is a two-electron process - the ions are produced immediately from the neutral atoms. It has been found for the first time that the resonant structure in A 2+ ion formation in such conditions is due to the excitation and ionization of neutral-atom mixed states. The atomic-state mixing in this case results from the Stark effect provided that the polarizability of these states is very high.

Boris Michailovich Smirnov