Spectroscopy of phenylacetylene bound to clusters of ammonia and the surface cluster analogy

Abstract

The results of a systematic study of the spectra shifts of the S1–S0 transition in phenylacetylene (PA) [1B2(1Lb)←1A1(1A)] due to solvation by NH3 are reported based on two-photon REMPI. A unique aspect of the present work is comparison of the red shifts for clusters produced by coexpansion techiques with those where PA is attached to performed ammonia clusters. In both experiments the 1–1 complex is red shifted by 80 cm−1. In the case of the coexpansion experiments the red shift is about 50 cm−1 for PA(NH3)n, n=2–7. By contrast, the clusters produced by attachment display a much different and gradually increasing red shift which saturates at 150 cm−1 for n=13 and beyond. Structural differences for clusters produced by the two different techniques are believed to be responsible.