VIBRATIONAL SPECTRA OF H3O+...Xn: INTERPLAY BETWEEN FERMI RESONANCE AND COMBINATION BAND

Solvation of H$_3$O$^+$ is an interesting and important problem in Chemical Physics. To gain a better understanding of the vibrational coupling in solvated H$_3$O$^+$, many studies using gas-phase Infra-Red Pre-Dissociation (IRPD) spectroscopy have been attempted. In experimental spectra of H$_3$O$^{+...}$Ar$_3$, a prounced splitting of O-H stretching near 3300 \wn is attributed to Fermi Resonance with overtone of bending. But a peculiar band at similar frequency observed in H$_3$O$^{+...}$(N$_2$)$_3$ has been assigned to be a combination band with hydrogen-bonded stretching modes. To gain further insight into the mechanism of these two types of anharmonic coupling, we have measured IRPD spectra of H$_3$O$^{+...}$Kr$_3$, and H$_3$O$^{+...}$(CO)$_3$. Ab Initio Anharmonic Algorithms have been applied to H$_3$O$^{+...}$X$_3$, (X=Ne, Ar, Kr, N$_2$, CO and H$_2$O) to examine the interplay between Fermi resonance and combination band