TAKAHASHI Y. Kyoto University, Department of Physics, Research Associate, 理学部, 助手 (40226907)
MIZUSAKI T. Kyoto University, Department of Physics, Assistant Professer, 理学部, 助教授 (20025448)
TSUNETO T. Kyoto University, Department of Physics, Professor, 理学部, 教授 (30025275)
|Budget Amount *help
¥6,900,000 (Direct Cost : ¥6,900,000)
Fiscal Year 1991 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1990 : ¥5,800,000 (Direct Cost : ¥5,800,000)
The purpose of the present work has been to study theoretically and experimentally the energy structure of the atoms such as alkali-metal atoms introduced as an Impurity In the superfluid helium, by using the techniques of laser spectroscopy. First of all, we studied the method of production of a large number of neutral atoms In the superfluid helium. Since there exists a difficulty In Introducing neutral atoms produced outside into liquid helium because of a strong exclusion force, we developed, at first, a new method, in which a sample solid material was put in the helium, and a pulsed YAG laser beam is focused to sputter. We found that the particles emitted from the surface of the sample were mostly clusters, so that another YAG laser beam was applied to dissociate the clusters to atoms and small molecules. By using method, a large number of neutral atoms can be produced in the superfluid helium, the number density being typically 10^9/cm^3. In order to obtain the excitation (absorption) and emission spectra of the produced atoms and molecules, cw tunable laser beam is applied, and the fluorescence was detected through a monochromator. We studied, at first, the alkali earth atoms such as barium and calcium, and could observe the excitation and emission spectra of both of single and triplet states. The most stricking results are such that the. excitation spectra are considerably blueshifted and broadened asymmetrically. On the contrary, the emission spectra are less affected by the liquid helium. These feature could be explain theoretically by using a simplified model. Withe respect to alkali-metal, we could not observe the atomic spectra, which are expected to be considerably red-shifted. However, we could observe, for the first time, the spectra of alkali-metal dimers such as Na_2 and Li_2. The vibrational structure of the electronic ground states were found to be approximately the same as those of free molecules.