One- and two-color (1 + 1) resonant ionization experiments were carried out for p-phenylenediamine (PD), N,N-dimethyl-p-phenylenediamine (DMPD), N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) under conditions of isolated molecules. An MPI ion-current spectrum of PD shows many sharp bands consisting of several vibrational progressions with the S1 origin (000) at 29 824 cm-1, while the photoelectron spectra due to the ground state (D0) of PD+ show a few progressions with the 0+ peak at 54 640 cm-1. All these progressions have been interpreted in terms of the ag vibrational modes in the S1 and D0 states of PD. The vibrational frequencies of the NH2 out-of-plane mode are 489 cm-1 (S0), 598 cm-1 (S1), and 1034 cm-1 (D0). An MPI spectrum of DMPD shows a well-resolved vibrational structure in the low-energy region and many congestion bands in the higher region; while that of TMPD shows no vibrational structure. These facts suggest that the geometrical changes in the S1 state increase with the number of CH3 groups. For a mixture of PD with acetonitrile in jets, a preliminary result supporting a molecular complex has been obtained, indicating a red shift of 207 cm-1 in the S1 region of PD and a progression of 24 cm-1, which is probably due to an intermolecular vibrational mode of the PD-acetonitrile complex.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry