title: Rovibrationally Excited Molecules on the Verge of a Triple Breakdown: Molecular and Roaming Mechanisms in the Photodecomposition of Methyl Formate.
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.
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Via Elce di Sotto 8, 06123 Perugia, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Lombardi
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Via Elce di Sotto 8, 06123 Perugia, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Palazzetti
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Via Elce di Sotto 8, 06123 Perugia, Italy.|Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche , Rome, Italy.|Instituto de Fisica, Universidade Federal da Bahia , Salvador, Brazil.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Aquilanti
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei 106, Taiwan.
authors.forename: Hou-Kuan
authors.initials: HK
authors.lastname: Li
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei 106, Taiwan.
authors.forename: Po-Yu
authors.initials: PY
authors.lastname: Tsai
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei 106, Taiwan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Kasai
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei 106, Taiwan.
authors.forename: King-Chuen
authors.initials: KC
authors.lastname: Lin