Vibrational relaxation process of Carbon Monoxide after the electronic excitation of (ClCO)2.

JUANA SALAS; LUCÍA LANFRI; MATIAS BERASATEGUI; ARGÜELLO, GUSTAVO A.; MAXI A. BURGOS PACI

Mendoza

Encuentro; 9th International meeting on photodynamics and related aspects,; 2016

UNSAM

The fragmentation of a bound molecule through absorption of one or more photonsis called photodissociation. The electromagnetic energy of the light beam isconverted into internal energy of the molecule by intramolecular transitions and ifthe transferred energy exceeds the binding energy of the weakest bond themolecule will irreversibly break apart.Photodissociation is a fantastic field for studying the internal dynamics ofpolyatomic molecules. In the last decades the interest on the study of primaryphotolysis processes of halogenated organic molecules has increased because of itsrelevance in atmospheric chemistry. In particular, time resolved spectroscopystudies allows to understand different aspects about photodissociation mechanisms.A specific experimental setup was used in order to detect the time resolved infraredfluorescence of ro-vibrationally excited carbon monoxide (CO*) originated from thephotolysis of (XCO)2-type molecules (where X can be either Cl or F). Suits and Lee 1,2studied the emission of CO* after the photolysis of (ClCO) 2 at different laserwavelengths namely, 193, 235 and 248 nm. They concluded that the energybalance for photolysis at 193 nm suggests that its mechanism of dissociation differfrom that at 248 nm. The present work is aimed to study the ro-vibrationalrelaxation of CO* after the photolysis of (ClCO) 2 at 266 nm using Nd:YAG laseroperating with the proper harmonic generator module.The characterization of the stable products of photodissociation was achieved bythe use of a FTIR spectrometer together with a mercury lamp emitting at 254 nm.The information obtained with this experiments along with the previous results,allowed us to propose a possible mechanism for the (XCO)2 photolysis at thiswavelength.The study of time-solved IR fluorescence confirmed the presence of vibrationallyexcited CO*. For this purpose, a cold gas filter containing CO was placed betweenthe emission source and the detector showing that calculated autoquenchingconstant is bigger than the one obtained without the filter. This result indicates thatCO* ( ν ≥1 ) is generated with the photolysis.[1] Chia-Yan Wu and Yuan-Pern Lee, J. Phys. Chem. Vol 107, 2389 (2003)[2] N. Hemmi and A. G. Suits, J. Phys. Chem. A 101, 6633 (1997).