Comparison of intensity distribution in the spectra of complex molecules cooled in a supersonic jet and in a crystalline matrix

Comparative investigations of intensity distribution in excitation and fluorescence spectra of 1,4-dihydroxyanthraquinone (quinizarin) and 1,4,5,8-tetrahydroxy-9,10-anthraquinone cooled in a supersonic jet and in a crystalline n-octane matrix were made. It is shown that in a jet the intensity distribution is appreciably affected by saturation effects. A special analysis of the effects has been made. It is noted that the investigation of saturation effects in jet spectra may serve as a tool for the lifetime measurements of the molecular excited states. In the absence of saturation, one has defined the constants of Franck-Condon and Herzberg-Teller interactions for the molecules under investigation. It has been established that the differences of intensity distribution in the spectra of molecules in a jet and in n-octane are mainly attributed to the Herzberg-Teller parameter variation.