Abstract

Laser-induced fluorescence (LIF) studies of impurity atoms dispersed in liquid helium have provided much insight into the microscopic structure of helium atoms surrounding the impurities. For example, a largely red-shifted and broadened emission spectrum of Ag atoms in liquid helium has been attributed to the formation of AgHe₂ exci-plexes.¹ On the other hand, heavy members of the group IIA atoms (Ca, Sr, and Ba) are known not to form metal-He_n exciplexes in their lowest singlet P-states. The lowest singlet emissions of those atoms show only small shifts and broadening² and have been semi-quantitatively explained by the so-called bubble model.³ However, we found that Mg and Be, the two lightest members of group IIA atoms, show quite anomalous LIF spectra in liquid helium.

© 1998 Optical Society of America