Laser Oscillation Characteristics and SCF-CI Calculations of a Cyanine Dye

Abstract

The laser spectrum, absorption and fluorescence spectra of a cyanine dye 3, 3'-diethyl-2, 2'-oxatricarbocyanine iodide were observed. On the other hand, the energy levels and oscillator strengths of the singlet state and the triplet state were calculated by applying the LCAO-SCF-CI method. And from both observed and calculated results, the relations between them were discussed.
The energy level difference between the singlet ground state S_O and the excited state S₁ was calculated to be 16652 cm^-1. The peak absorption spectrum was estimated at about 16556 cm^-1 in an ethanol solution based on the experimental value with additional consideration of the solvent effect. And a fairly good agreement was obtained between the calculated and experimental values. The oscillator strength was 2.427 for the S_O-S₁ transition which was found dominant. Hence, the good pumping efficiency was considered this dye. The difference in energy level between the excited state S₁ and the triplet state T₁ was 12514 cm^-1.
This large difference suggests a small interaction between singlet and triplet states, and further could be estimated a high efficiency in laser oscillation.