Physical Review Letters. - 2005, vol. 94, p. 063001
English
We have observed several new spectral features in the fluorescence of cesium atoms implanted in the hcp phase of solid helium following laser excitation to the 6²P states. Based on calculations of the emission spectra using semi empirical Cs-He pair potentials the newly discovered lines can be assigned to the decay of specific Cs*He(n) exciplexes: an apple-shaped Cs(AП(3/2))He₂ and a dumbbell-shaped Cs(AП(1/2))He(n) exciplex with a well-defined number n of bound helium atoms. While the former has been observed in other environments, it was commonly believed that exciplexes with n>2might not exist. The calculations suggest Cs(AП(1/2))He₇ to be the most probable candidate for that exciplex, in which the helium atoms are arranged on a ring around the waist of the dumbbell-shaped electronic density distribution of the cesium atom.