Theoretical and REMPI spectroscopic study on phenylhydrazine and phenylhydrazine-(Ar)n (n=1, 2) van der Waals complexes

Phenylhydrazine and its van der Waals complexes with one or two argon atoms were investigated with theoretical calculations and resonant two photon ionization (R2PI) spectroscopy. The ab initio and DFT calculations found a conversion of the orbital hybridization of the N-beta atom from sp(3)-like in the S-0 state to sp(2)-like in the S-1 state, suggesting that the lone pair electrons of the N-beta atom are involved in a super p-p-pi conjugation over the skeleton of phenylhydrazine in the S-1 state. The structural change of the hydrazino group in the S-1 <- S-0 electronic transition was reflected by the vibrational excitations of the hydrazino group observed in the 1C-R2PI spectrum. The band origin of the S-1 <- S-0 transition is determined to be 33610 cm(-1) and the adiabatic ionization energy (IE) of phenylhydrazine, measured by 2C-R2PI spectroscopy, is 62829 +/- 15 cm(-1). The S-1 <- S-0 electronic transitions of phenylhydrazine-Ar and phenylhydrazine-Ar-2 complexes were also observed in the 1C-R2PI spectrum, and their band origins are, respectively, red-shifted by 39 and 80 cm(-1) from that of phenylhydrazine.