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

LANFRI, LUCIA; ARGÜELLO, GUSTAVO; SALAS, JUANA; BURGOS, MAXI; BERASATEGUI, MATIAS

Mendoza

Congreso; 9th INTERNATIONAL MEETING ON PHOTODYNAMICS AND RELATED ASPECTS; 2016

The fragmentation of a molecule through absorption of one or more photons is called photodissociation. The electromagnetic energy of the light beam is converted into internal energy of the molecule by intramolecular transitions and if the transferred energy exceeds the binding energy of the weakest bond the molecule will break apart.Photodissociation is a fantastic field for studying the internal dynamics of polyatomic molecules. In the last decades the interest on the study of primary photolysis processes of halogenated organic molecules has increased because of its relevance in atmospheric chemistry. In particular, time resolved spectroscopy studies allows to understand different aspects about photodissociation mechanisms.A specific experimental setup was used in order to detect the time resolved infrared fluorescence of ro-vibrationally excited carbon monoxide (CO*) originated from the photolysis of (ClCO)2 molecules. Suits and Lee1,2 studied the emission of CO* after the photolysis of (ClCO)2 at different laser wavelengths namely, 193, 235 and 248 nm. They concluded that the energy balance for photolysis at 193 nm suggests that its mechanism of dissociation differ from that at 248 nm. The present work is aimed to study the ro- vibrational relaxation of CO* after the photolysis of (ClCO)2 at 266 nm using Nd:YAG laser operating with the proper harmonic generator module.The characterization of the stable products of photodissociation was achieved by the 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 (ClCO)2 photolysis at this wavelength.The study of time-solved IR fluorescence confirmed the presence of vibrationally excited CO*. For this purpose, a cold gas filter containing CO was placed between the emission source and the detector showing that calculated autoquenching constant is bigger than the one obtained without the filter. This result indicates that CO* (ν ≥ 1) is generated with the photolysis.Deactivation of the IR fluorescence was performed with O2, CO2 and CO as quenchers. It was found that the energy-transfer process was very efficient for CO and that for CO2 other relaxation process take place, being CO2 better quenching than CO. For pressures bigger than 10 mbar, reactive processes are observed generating CO2 as one of the products which acts as quencher.