Diode laser slit-jet spectra and analysis of the m 14 fundamental of 1-chloro-1,1-difluoroethane (HCFC-142b) Giuseppe DÕAmico a, * and Marcel Snels b a Istituto di Metodologie Inorganiche e dei Plasmi, Sezione di Potenza, CNR Zona Industriale, 85050 Tito Scalo, (PZ), Italy b Istituto di Scienze dell’Atmosfera e del Clima, Sezione di Roma, CNR Via Fosso del Cavaliere 100, 00133 Roma, Italy Received 12 July 2002; in revised form 10 September 2002 Abstract High resolution infrared spectra (0.001cm 1 FWHM) have been measured for mixtures of 1-chloro-1,1-difluoroethane in Ne, expanded in a supersonic planar jet. The m 14 fundamental has been analyzed for both isotopic species, CH 3 CF 2 35 Cl and CH 3 CF 2 37 Cl. Ó 2002 Elsevier Science (USA). All rights reserved. Keywords: Diode laser slit-jet; HCFC-142b 1. Introduction 1-Chloro-1,1-difluoroethane (HCFC-142b) is one of themostimportanthydrochlorofluorocarbons(HCFCs) whichhavebeenintroducedduringthelastdecadesasa replacement of the well known chlorofluorocarbons (CFCs), whose production has been progressively re- duced as a result of the application of the Montreal Protocol(1987)anditsamendments(London,1990and Copenhagen 1992). Whereas the CFCs are mostly de- stroyed by solar UV radiation in the stratosphere, the HCFC molecules contain one or more hydrogen atoms and react with tropospheric OH radicals. Therefore the HCFCs have a shorter atmospheric lifetime (about 20 years for HCFC-142b [1], with respect to the 50 years for CFC-11 and 100 years for CFC-12) and as a con- sequence a lower ozone depletion potential than the CFCs. However, HCFCs are strong absorbers in the infrared and contribute to the global warming. Indeed, some HCFCs have a global warming potential which is comparable or even higher than that of the CFCs [2]. Sincetheirintroduction,theglobalmixingratiosforthe HCFCs are steadily increasing [3], although they are much lower than those of the CFCs. For HCFC-141b andHCFC-142bglobalmixingratiosof0.7and4.3ppt, respectively, have been measured [4] in 1993, with an increaserateof0.9and1.1pptperyear. Infrared spectroscopy is a powerful tool for moni- toring trace gases in the atmosphere and spectroscopic investigations of the most important HCFCs are re- quired for supporting the detection and quantification of HCFCs in the atmosphere. The infrared absorption spectra of CFCs and HCFCs are often rather complex, duetothehighlinedensityandthelimitedinstrumental resolution. The presence of hot-bands and different chlorine isotopic species renders the analysis even more troublesome. We have previously demonstrated [5–9] that the diode laser slit-jet technique, which combines high resolution (0.001cm 1 typically) with low rota- tional and vibrational temperatures, can simplify the spectra enormously, allowing for unambiguous assign- ments and successful analyses. Here the analysis of the m 14 band of HCFC-142b is presented, showing the po- tential of this method, allowing for a straightforward assignment of well resolved lines of both isotopic spe- cies, CH 3 CF 2 35 ClandCH 3 CF 2 37 Cl. Journal of Molecular Spectroscopy 217 (2003) 72–78 www.elsevier.com/locate/jms * Corresponding author. Current address: Dipartimento di Scienze Fisiche Universita ´ di Napoli ‘‘Federico II,’’ Complesso Universitario di M.S. Angelo, I-80126 Napoli, Italy. Fax: +39-06-4993421. E-mail addresses: damico@ims.pz.cnr.it (G. DÕAmico), m.snels@ isac.cnr.it (M. Snels). 0022-2852/02/$ - see front matter Ó 2002 Elsevier Science (USA). All rights reserved. PII:S0022-2852(02)00017-6