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New experiments and assignments of the torsional spectrum of dimethyl-ether

AutorFernández Sánchez, José María ; Tejeda, Guzmán ; Carvajal, M.; Senent, María Luisa
Fecha de publicación21-nov-2016
CitaciónECLA (2016)
ResumenWe present new Raman spectra of dimethyl-ether (DME) and of 13C-DME at room temperature, and of cooled DME in supersonic jet. The spectral region of the torsional overtones of DME is rather complex due to their coupling with the C-O-C bending mode, and the presence of many hot bands. The spectrum of cooled DME allowed us to assign unequivocally the torsional overtones and their first hot bands. Dimethyl-ether (DME) is a molecule found in star-forming regions, where it plays an important role in astrochemical processes [1]. Mono-deuterated DME [2] and singly substituted 13C-DME [3] have been detected as well. Despite this astrophysical interest, there is a lack of accurate spectral data of its isotopic species, which impedes further identification in the interstellar medium. The absorption spectrum of DME is quite dense and its analysis challenging because DME is an asymmetric top molecule with two internal rotors undergoing large amplitude motions. Thus, understanding such large amplitude internal motions on a quantitative level rely on quantum chemical models validated by laboratory data. However, one of the torsional bands is forbidden in the infrared spectra, that preventing the experimental determination of some of the interaction parameters. We have recorded the Raman spectra of DME and of 13C-DME at room temperature, and of cooled DME in supersonic jet. We will introduce first the experimental approach [4, 5], and then we will present some Raman spectra of DME at different spectral regions. The spectral region of the torsional overtones of DME is rather complex due to their coupling with the C-O-C bending mode, and the presence of many hot bands. The spectrum of cooled DME allowed us to assign unequivocally the torsional overtones and their first hot bands, amending previous assignment from the literature [6]. In turn, the observed frequencies have been used to refine 3-D quantum calculations employing a torsion-torsion-bending Hamiltonian [7], along with an ab initio potential surface [8]. References [1] Garrod, R. T.; Widicus-Weaver, S. L.; Herbst, E., Astrophysical Journal 682 (2008) 283. [2] Richard, C.; Margul`es, L.; Caux, E.; et al., Astronomy & Astrophysics 552 (2013) A117. [3] Bisschop, S. E.; Schilke, P.; Wyrowski, F.; et al., Astronomy & Astrophysics 552 (2013) A122. [4] Tejeda, G.; Fern¿andez-S¿anchez, J. M.; Montero, S., Applied Spectroscopy 51 (1997) 265. [5] Fernandez, J. M.; Montero, S., Journal of Chemical Physics 118 (2003) 2657. [6] Groner, P.; Durig, J. R., Journal of Chemical Physics 66 (1977) 1856. [7] Villa, M.; Senent, M. L.; Dominguez-Gomez, R.; Alvarez-Bajo, O.; Carvajal, M., Journal of Physical Chemistry A 115 (2011) 13573. [8] Carvajal, M.; Alvarez-Bajo, O.; Senent, M. L.; Dominguez-Gomez, R.; Villa, M., Journal of Molecular Spectroscopy 279 (2012) 3.
DescripciónEuropean Conference on Laboratory Astrophysics: Gas on the rocks, CSIC, Madrid, Spain; 21-25 November, 2016 ; http://www.ecla2016.com/
URIhttp://hdl.handle.net/10261/155421
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