Emission spectra ofRb*Henexciplexes in a cold

Rb*Henexciplexes in solidHe4

“…8 are stable, so once the Rb * He n=1 exciplex is created all larger complexes can be formed with high probability by the sequential filling of the helium ring until the state with the lowest binding energy is reached. In helium environments with lower densities than pressurized solid helium the time intervals between successive attachments is long enough to permit the exciplex to fluoresce, so that fluorescence from all intermediate exciplexes Rb * He n=1...6 can be observed in gaseous helium [2]. The results presented below indicate that in solid He the Rb(A 2 Π 1/2 )He n formation process is so rapid that any intermediate configurations have no time to emit fluorescence.…”

“…These studies have given support to earlier proposals [4,5], which tentatively explained the quenching of atomic fluorescence from light alkali atoms (Li, Na, K) in condensed helium by the formation of alkali-helium exciplexes, whose emission spectra are strongly red-shifted with respect to the atomic resonance lines. Exciplex formation was also studied on the surface of helium nanodroplets [6,7,8,9,10] and in cold helium gas [1,2,11]. Recently we have performed an experimental and theoretical study of the Cs * He n exciplex formation process in the hcp and bcc phases of solid 4 He [12].…”

“…Recently we have performed an experimental and theoretical study of the Cs * He n exciplex formation process in the hcp and bcc phases of solid 4 He [12]. A comparison with the results of [1,2] has revealed that the exciplex formation mechanism in solid helium differs from the one in superfluid helium and in cold helium gas. We concluded that exciplexes in solid helium result from the collective motion of several nearby helium atoms which approach the Rb atom simultaneously, while in liquid and gaseous helium the binding of the helium atoms proceeds in a time sequential way.…”

“…The formation process of alkali-He n exciplexes, i.e., of bound states of an excited alkali atom with one or more ground state helium atoms, was studied in recent years in superfluid [1,2] and in solid [3] helium. These studies have given support to earlier proposals [4,5], which tentatively explained the quenching of atomic fluorescence from light alkali atoms (Li, Na, K) in condensed helium by the formation of alkali-helium exciplexes, whose emission spectra are strongly red-shifted with respect to the atomic resonance lines.…”

Spectroscopy of alkali-metal atoms in dense supercritical4He at low temperatures

“…These quasimolecular structures arising from the highly anisotropic alkali-metal-helium interaction have been analyzed in detail in [25,[38][39][40][41]. The dependence of the exciplex populations on He temperature and density in the range of ρ 0 = 10 18 -10 19 cm −3 was studied experimentally in [38,42]. Neglecting the population of the exciplex states, especially those in the B 3/2 electronic state, leads mainly to a discrepancy between the experimental and calculated spectra in the range of 930-980 nm (see Fig.…”