Optical properties of impurity atoms in pressurized superfluid helium

Atomic and molecular defects in solid 4He

“…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. In other experiments [122,123,44,74,45,94] the same effect was achieved by increasing the repetition rate of the ablation laser up to 1 kHz.…”

“…Extensive calculations of the atomic bubbles formed by alkali (Rb and Cs) atoms in liquid He were reported by Kinoshita et al [44][45][46]. The authors used an expansion of the perturbed electronic wavefunctions of the dopant's valence electron in the basis of unperturbed |L, M L , S, M S states including only the lowest nS and nP states.…”

“…In order to calculate the lineshapes of the optical absorption lines of atomic bubbles, the following procedure has been applied [42][43][44][45]55,48]. The broadening of the atomic spectral lines is attributed to the spatial extension of the electronic wavefunctions due to radial (breathing mode) bubble oscillations.…”

“…The first experiments with atomic barium in solid He [67,57] showed that this conclusion also holds for atomic bubbles. However, detailed studies of the absorption and emission spectra of Cs atoms in liquid [44][45][46] and in solid [51,68,48] helium revealed a number of well pronounced effects that occur at the liquid-solid phase transition as well as at the transition from the body-centered cubic (bcc) to the hexagonal close-packed (hcp) crystalline phase. Analyzing the observed discontinuity of the 6S 1/2 → 6P 1/2 transition wavelength at the liquid-bcc phase boundary, we have adapted the liquid atomic bubble model to bubbles in solid He [48] by a characteristic new term in the expression for the bubble energy.…”

“…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.…”