High Resolution Laser Spectroscopy of Small Molecules and Clusters.

This thesis consists of two parts. The first part is an investigation of the low lying triplet states of strontium oxide (SrO). SrO is produced in the gas phase. Laser spectroscopic studies of the band system near 596 nm revealed transitions in the triplet system. From the spectroscopic data obtained we were able to detect 3 triplet states that had not been observed so far but were predicted by theoretical studies. Two ^3II states were observed around 26000 cm^{-1} and were labeled f^3II and g ^3II respectively. Both states showed fluorescence into the a^3II state, into the ground state (X^1Sigma) and into a new ^3Sigma^{+} state as well. This state was called b ^3Sigma^{+} by analogy to calcium oxide. For high rotational quantum numbers J perturbations in the g^3{rm II}_2-a^3{rm II}_2 transitions were observed. A combined fit of the f^3{rm II }_1-a^3{rm II}, g^3{rm II} _2-a^3{rm II}, g^3{rm II}_2 -b^3Sigma^{+}, f^3{rm II}_1 -b^3Sigma^{+}, f^3{rm II}_1 -X^1Sigma^{+}, and g^3{rm II}_2 -X^1Sigma^{+} transitions led to spectroscopic constants for the three new triplet states (f, g, and b) as well as an improvement of the spectroscopic constants for the a ^3{rm II} state. The second part of this thesis investigates clusters of type M_{rm n}{rm X}_{rm m} (M metal, X halogen or oxygen), which have defects or color centers. For Na_2{rm F} the ionization potential was determined. In addition an optical absorption band around 2 eV was investigated. Evidence was found that Na_3 clusters are necessary in order to produce Na_3{rm O } The absorption band of Na_3 {rm O} around 2 eV was recorded.