Spectroscopy and dynamics of neutral atoms in superfluid helium

Atomic and molecular defects in solid 4He

“…As a consequence the absorption line profile calculated in [59] is composed of five overlapping components and has a spectral shift and a total width close to those of the experimental lineshape from [154]. The authors of [59] also reported a calculation of the absorption spectrum of the 3P − 4S transition that strongly underestimates the blueshift observed in experiment [125].…”

“…A similar behavior was observed in the earlier work [116] on Ba + ions. The n 2 S 1/2 − n 2 P 1/2,3/2 transitions of silver in bulk liquid helium [125] and in He nanodroplets [151,152] also show very similar spectral profiles of the absorption lines. The D 2 transition is split in two partially resolved components separated by approximately 500 cm −1 .…”

“…An important advantage of the latter method is its applicability to pressurized liquid and even solid He. It has been applied by several groups investigating alkali [122,123,44,74,45,94] and alkaline-earth elements [124,125,57,85,56], as well as Ag [100], Al, Yb, Ga, and In [124]. Since the laser ablation in liquid He produces mostly impurity clusters, [124,121,58,56] a second delayed laser pulse was applied in some experiments in order to dissociate the clusters and to produce individual impurity atoms.…”

Spectroscopy of barium atoms in liquid and solid helium matrices

“…Electronically excited Ba atoms at densities of ≈10 8 cm −3 were produced by the recombination of implanted Ba + ions with free electrons in the liquid helium bath, and the spectrum of the recombination-induced fluorescence was observed. Larger dopant densities (up to 10 10 cm −3 ) were obtained by producing Ba atoms via direct laser ablation in liquid helium, close to the observation zone [7][8][9][10]. Those studies focused on the laser-induced fluorescence (LIF) and excitation spectra of the singlet 6s 2 -6s6p transition and of the triplet 5d6s -5d6p transitions whose lowest state is the metastable 5d6s 3 D 1 .…”

Lifetime of the Cs 6P1/2 state in bcc and hcp solid 4He

“…No time dependent studies of alkalis in solid He have been reported so far, although excited state lifetimes of Rb and Cs immersed in superfluid He have been studied in the past [8,9]. Those experiments had revealed some interesting observations: while the Cs 6P 1/2 lifetime was found to be pressure independent up to the solidification point, with a value below the free atomic lifetime, the lifetime of the corresponding 5P 1/2 state of Rb decreases with increasing pressure, leading to a complete quenching of the fluorescence.…”