The excitation and emission spectra of alkali-metal atoms (Cs and Rb) in liquid helium are studied. The helium pressure is changed from the saturated vapor pressure to about 25 atm at 1.6 K, under which conditions the liquid helium is in a superfluid state. The pressure shift and broadening of the observed spectra corresponding to the D lines are explained qualitatively by a theoretical calculation based on the spherical atomic bubble model. The Cs ${\mathit{D}}_{2}$ excitation spectra are found to have double peaks, indicating the existence of anisotropic oscillations of the bubble surface. The disappearance of the ${\mathit{D}}_{2}$ emission lines and the pressure-dependent quenching of the Rb ${\mathit{D}}_{1}$ emission lines are also discussed.The excitation and emission spectra of alkali-metal atoms (Cs and Rb) in liquid helium are studied. The helium pressure is changed from the saturated vapor pressure to about 25 atm at 1.6 K, under which conditions the liquid helium is in a superfluid state. The pressure shift and broadening of the observed spectra corresponding to the D lines are explained qualitatively by a theoretical calculation based on the spherical atomic bubble model. The Cs ${\mathit{D}}_{2}$ excitation spectra are found to have double peaks, indicating the existence of anisotropic oscillations of the bubble surface. The disappearance of the ${\mathit{D}}_{2}$ emission lines and the pressure-dependent quenching of the Rb ${\mathit{D}}_{1}$ emission lines are also discussed.

Physical Review AOct 1, 199571 citations

Pressure-dependent quenching of Rb 5Pstates in liquid helium

Toshiya Kinoshita, K. Fukuda, T. Matsuura +1 more

The decay times of ${\mathit{D}}_{1}$ emission lines of Rb and Cs atoms in superfluid helium were measured at 1.6 K as functions of helium pressure in a range from the saturated vapor pressure to about 25 atm. In the case of Cs, the measured decay time is almost independent of the helium pressure and is given by the lifetime of the 6 ${\mathit{P}}_{1/2}$ state of the free atom. However, we have found that the decay time of the Rb ${\mathit{D}}_{1}$ line decreases with increasing pressure. This suggests the coexistence of two processes leading from the excited P state to the ground state, one an ordinary ${\mathit{D}}_{1}$ emission transition and the other a process decaying via a lower energy state before reaching the ground state. The pressure-dependent quenching observed only for the Rb atom can be explained by the competition of the above two processes. A possible mechanism for quenching of the Rb 5P states is discussed in terms of the interaction potentials of the alkali-metal-atom-- ${\mathrm{He}}_{\mathit{N}}$ system, where two or six helium atoms are localized near the alkali core in a particular anisotropic configuration. The dynamics of processes leading from the excited P states of Na and Cs atoms are also discussed. \textcopyright{} 1996 The American Physical Society.The decay times of ${\mathit{D}}_{1}$ emission lines of Rb and Cs atoms in superfluid helium were measured at 1.6 K as functions of helium pressure in a range from the saturated vapor pressure to about 25 atm. In the case of Cs, the measured decay time is almost independent of the helium pressure and is given by the lifetime of the 6${\mathit{P}}_{1/2}$ state of the free atom. However, we have found that the decay time of the Rb ${\mathit{D}}_{1}$ line decreases with increasing pressure. This suggests the coexistence of two processes leading from the excited P state to the ground state, one an ordinary ${\mathit{D}}_{1}$ emission transition and the other a process decaying via a lower energy state before reaching the ground state. The pressure-dependent quenching observed only for the Rb atom can be explained by the competition of the above two processes. A possible mechanism for quenching of the Rb 5P states is discussed in terms of the interaction potentials of the alkali-metal-atom--${\mathrm{He}}_{\mathit{N}}$ system, where two or six helium atoms are localized near the alkali core in a particular anisotropic configuration. The dynamics of processes leading from the excited P states of Na and Cs atoms are also discussed. \textcopyright{} 1996 The American Physical Society.

Physical Review AJun 1, 199634 citations

Stabilization of nitrogen atoms in superfluid helium

Eugene B. Gordon, Леонид Павлович Межов-Деглин, O. F. Pugachev

Jan 20, 197421 citations

Nonlinear Variation of Light-Pressure-Induced Multilevel Atomic Line Shifts with Vapor Pressure in Helium Spectroscopy

Tanya Zelevinsky

This paper has been temporarily withdrawn. Highly nonlinear dependences of 4He 2^3S - 2^3P lines on pressure were observed in vapor cell saturation spectroscopy. Line shifts agree with those expected from light-pressure-induced perturbation of atomic velocity distribution. In the lin-perp-lin pump and probe polarization configuration, multilevel atomic structure must be taken into account. For a two-level atom, the shift magnitude is determined by the collisional time constant, but when the system has dark states there is an additional time constant due to optical pumping. The collisional and optical time constants compete, and become equal at a certain pressure p_0. Saturation signal vanishes at p_0 whereas signal due to light pressure remains. This leads to a dependence of line centers on pressure that exhibits apparently singular behavior at p_0. The 2S - 2P(J=1) line shift reaches the natural half width. Vapor cells may be more suitable for investigation of this effect than atomic beams since the shifts vanish at sufficiently high pressures. Two ways of controlling the shifts for the helium 2P fine structure measurement are discussed.This paper has been temporarily withdrawn. Highly nonlinear dependences of 4He 2^3S - 2^3P lines on pressure were observed in vapor cell saturation spectroscopy. Line shifts agree with those expected from light-pressure-induced perturbation of atomic velocity distribution. In the lin-perp-lin pump and probe polarization configuration, multilevel atomic structure must be taken into account. For a two-level atom, the shift magnitude is determined by the collisional time constant, but when the system has dark states there is an additional time constant due to optical pumping. The collisional and optical time constants compete, and become equal at a certain pressure p_0. Saturation signal vanishes at p_0 whereas signal due to light pressure remains. This leads to a dependence of line centers on pressure that exhibits apparently singular behavior at p_0. The 2S - 2P(J=1) line shift reaches the natural half width. Vapor cells may be more suitable for investigation of this effect than atomic beams since the shifts vanish at sufficiently high pressures. Two ways of controlling the shifts for the helium 2P fine structure measurement are discussed.

arXiv:physics/0401075Jan 15, 20040 citations

Microscopic Theory of Superfluid Helium

Pierre C. Hohenberg, Paul C. Martin

Annals of PhysicsApr 1, 200011 citations

{\mathit{D}}_{2}

excitation spectra are found to have double peaks, indicating the existence of anisotropic oscillations of the bubble surface. The disappearance of the

{\mathit{D}}_{2}

emission lines and the pressure-dependent quenching of the Rb

{\mathit{D}}_{1}

emission lines are also discussed.

The decay times of

{\mathit{D}}_{1}

emission lines of Rb and Cs atoms in superfluid helium were measured at 1.6 K as functions of helium pressure in a range from the saturated vapor pressure to about 25 atm. In the case of Cs, the measured decay time is almost independent of the helium pressure and is given by the lifetime of the 6

{\mathit{P}}_{1/2}

state of the free atom. However, we have found that the decay time of the Rb

{\mathit{D}}_{1}

line decreases with increasing pressure. This suggests the coexistence of two processes leading from the excited P state to the ground state, one an ordinary

{\mathit{D}}_{1}

emission transition and the other a process decaying via a lower energy state before reaching the ground state. The pressure-dependent quenching observed only for the Rb atom can be explained by the competition of the above two processes. A possible mechanism for quenching of the Rb 5P states is discussed in terms of the interaction potentials of the alkali-metal-atom--

{\mathrm{He}}_{\mathit{N}}

system, where two or six helium atoms are localized near the alkali core in a particular anisotropic configuration. The dynamics of processes leading from the excited P states of Na and Cs atoms are also discussed. \textcopyright{} 1996 The American Physical Society.