Rovibrationally Excited Molecules on the Verge of a Triple Breakdown: Molecular and Roaming Mechanisms in the Photodecomposition of Methyl Formate
Journal
Journal of Physical Chemistry A
Journal Volume
120
Journal Issue
27
Pages
5155-5162
Date Issued
2016
Author(s)
Lombardi, A.
Palazzetti, F.
Aquilanti, V.
Li, H.-K.
Tsai, P.-Y.
Kasai, T.
Lin, K.-C.
Abstract
For the photodissociation of the simplest of esters, methyl formate HCOOCH3, the energy threshold for triple fragmentation into H, CH3O, and CO was measured by previous ion-imaging experiments at a sequence of wavelengths. The translational energy features of product CO in the ground vibrational level (υ = 0) and for selected rotational states were characterized. In this integrated experimental and theoretical approach (i) the focus is at a laser energy barely below that threshold; (ii) Fourier-transform infrared emission spectroscopy measurements probe the rovibrational energy deposition in CO(υ) for υ > 0 and the emergence of the roaming phenomenon; (iii) accompanying quantum chemical calculations describe the selective rupture of bonds; and (iv) molecular dynamics simulations of dissociation are performed, introducing an approach explicitly involving outcomes from paths originated nonadiabatically through conical intersections. Quantitative information on energy disposal is provided: we found extensive vibrational excitation of CO, while rotational bands are colder and bimodal, due to contributions from direct and roaming modes.
SDGs
Type
journal article