Characterization and vibrationally mediated photodissociation of jet-cooled formic acid dimer and phenol-carbon monoxide complexes.

摘要

Vibrational action spectroscopy of jet-cooled formic acid dimer measures the frequency of the C-H(D) stretching vibration and its coupling to nearby states. The action spectrum of (DCOOH)2 reveals a specific Fermi resonance between the C-D stretch and two antisymmetric combination states formed from the C-O stretch and DCO bend. A three-state deperturbation analysis shows that there is a relatively strong coupling between the fundamental vibration and each of the combination vibrations (|13 cm-1|) and between the combination states themselves (|7 cm-1|). This situation contrasts with that for the action spectrum of (HCOOD)2, where the C-H oscillator is isolated and not strongly coupled to other states.;We also study the photodissociation dynamics of the H(D)-atom formation channels of jet-cooled formic acid dimer. Electronic action spectra with or without initial vibrational excitation maps the dimer absorption spectrum at total energies up to 45 000 cm-1. Beyond 45 000 cm -1, deuterium production decreases significantly, suggesting another product channel opening. Kinetic energy distributions of the D atoms formed by one-photon dissociation of (DCOOH)2 suggest the C-D bond breakage is similar to those of the monomer. This contrasts the kinetic energy distributions of the H atoms formed by one-photon dissociation of (DCOOH)2 and H-yield upon initial excitation of the O-H stretching transition, which both suggest dynamics affected by the dimerization.;In order to study the dynamics of phenol-carbon monoxide and distinguish between the complex and bare phenol, we characterize the complex by reproducing the (1+1') resonance enhanced multiphoton ionization (REMPI) spectrum and by reproducing the jet-cooled O-H vibrational spectrum of the complex. Initial measurements of the infrared action spectrum of phenol-carbon monoxide show that the action spectrum is similar to the REMPI spectrum measured without vibrational excitation, suggesting the vibrational excitation has little or no effect on the complex dynamics.