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dc.contributor.authorNishida, Junen_US
dc.contributor.authorShigeto, Shinsukeen_US
dc.contributor.authorYabumoto, Sohshien_US
dc.contributor.authorHamaguchi, Hiro-oen_US
dc.date.accessioned2014-12-08T15:29:39Z-
dc.date.available2014-12-08T15:29:39Z-
dc.date.issued2012-12-21en_US
dc.identifier.issn0021-9606en_US
dc.identifier.urihttp://dx.doi.org/10.1063/1.4770264en_US
dc.identifier.urihttp://hdl.handle.net/11536/21298-
dc.description.abstractCombination bands that involve CH- or OH-stretch vibrations appear in the near-infrared (NIR) region (4000-10 000 cm(-1)). Because they arise from anharmonic coupling between the component fundamentals, detailed analysis of the frequency and intensity of NIR combination bands allows one to elucidate the mechanisms behind the vibrational coupling in the condensed phase in terms of mechanical and electrical anharmonicities. Nevertheless, little has been studied, in particular experimentally, on the origin of the combination band intensity. Here, we show that NIR electroabsorption (EA) spectroscopy, which directly probes the effects of an externally applied electric field on a combination band, can shed new light on anharmonic vibrational coupling through determination of the direction of the transition moment for the combination band. We studied the combination band of the CH-stretch (nu(1)) and CH-bend (nu(4)) modes of liquid chloroform. The electric-field induced absorbance change of the nu(1) + nu(4) combination band caused by reorientation of the chloroform molecule was measured at various chi angles, where chi is the angle between the direction of the applied electric field and the polarization of the incident IR light. We were able to detect an absorbance change as small as 5 x 10(-8) for the combination band. Using the NIR EA spectra of the combination band together with those of the CH-stretch and bend fundamentals, the angle between the transition moment for the combination band and the permanent dipole moment was determined experimentally for the first time to be (79 +/- 14)degrees. The present investigation indicates that the contribution of the CH-stretch mode to the mechanical anharmonicity is minor and that the CH-bend mode plays a dominant role in the mechanical part of the vibrational coupling between the two fundamentals. Furthermore, density functional theory calculations show that both the mechanical anharmonicity of the CH-bend mode and the electrical anharmonicity may contribute equally to the anharmonic coupling. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4770264]en_US
dc.language.isoen_USen_US
dc.subjectdensity functional theoryen_US
dc.subjectinfrared spectraen_US
dc.subjectorganic compoundsen_US
dc.subjecttransition momentsen_US
dc.subjectvibrational modesen_US
dc.titleAnharmonic coupling of the CH-stretch and CH-bend vibrations of chloroform as studied by near-infrared electroabsorption spectroscopyen_US
dc.typeArticleen_US
dc.identifier.doi10.1063/1.4770264en_US
dc.identifier.journalJOURNAL OF CHEMICAL PHYSICSen_US
dc.citation.volume137en_US
dc.citation.issue23en_US
dc.citation.epageen_US
dc.contributor.department應用化學系zh_TW
dc.contributor.department應用化學系分子科學碩博班zh_TW
dc.contributor.departmentDepartment of Applied Chemistryen_US
dc.contributor.departmentInstitute of Molecular scienceen_US
dc.identifier.wosnumberWOS:000312780300028-
dc.citation.woscount0-
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