Browsing by Author "Yabumoto, Sohshi"

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Anharmonic coupling of the CH-stretch and CH-bend vibrations of chloroform as studied by near-infrared electroabsorption spectroscopy
(2012-12-21)
Nishida, Jun
;
Shigeto, Shinsuke
;
Yabumoto, Sohshi
;
Hamaguchi, Hiro-o
;
應用化學系
Combination 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]
Automatic and objective oral cancer diagnosis by Raman spectroscopic detection of keratin with multivariate curve resolution analysis
(2016-01-25)
Chen, Po-Hsiung
;
Shimada, Rintaro
;
Yabumoto, Sohshi
;
Okajima, Hajime
;
Ando, Masahiro
We have developed an automatic and objective method for detecting human oral squamous cell carcinoma (OSCC) tissues with Raman microspectroscopy. We measure 196 independent Raman spectra from 196 different points of one oral tissue sample and globally analyze these spectra using a Multivariate Curve Resolution (MCR) analysis. Discrimination of OSCC tissues is automatically and objectively made by spectral matching comparison of the MCR decomposed Raman spectra and the standard Raman spectrum of keratin, a well-established molecular marker of OSCC. We use a total of 24 tissue samples, 10 OSCC and 10 normal tissues from the same 10 patients, 3 OSCC and 1 normal tissues from different patients. Following the newly developed protocol presented here, we have been able to detect OSCC tissues with 77 to 92% sensitivity (depending on how to define positivity) and 100% specificity. The present approach lends itself to a reliable clinical diagnosis of OSCC substantiated by the "molecular fingerprint" of keratin.
Nanosecond Time-resolved Infrared Spectra and Structure of the Charge-transfer State of 9,9 '-Bianthryl in Acetonitrile
(2012-06-05)
Asami, Nobuyuki
;
Yabumoto, Sohshi
;
Shigeto, Shinsuke
;
Takaya, Tomohisa
;
Hamaguchi, Hiro-o
Nanosecond time-resolved infrared spectra of photoexcited 9,9'-bianthryl (BA) and its deuterated derivative (BA-d(18)) were recorded in acetonitrile-d(3) and cyclohexane-d(12). The charge-transfer (CT) bands observed at the 1200-1400 cm(-1) region are contributed mostly by the intra- and inter-ring CC stretch vibrations. The intrinsic frequency of the inter-ring CC stretch falls within the 1200-1400 cm(-1) region, which is consistent more with a twisted structure than with a fully conjugated planar structure of the CT state.
Ordering, Interaction, and Reactivity of the Low-Lying n pi* and pi pi* Excited Triplet States of Acetophenone Derivatives
(2010)
Yabumoto, Sohshi
;
Shigeto, Shinsuke
;
Lee, Yuan-Pern
;
Hamaguchi, Hiro-o
;
應用化學系
Tilted Two-Dimensional Array Multifocus Confocal Raman Microspectroscopy
(2017-07-18)
Yabumoto, Sohshi
;
Hamaguchi, Hiro-o
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
A simple and efficient two-dimensional multi focus confocal Raman microspectroscopy featuring the tilted array, technique is demonstrated. Raman scattering from a 4 X 4 square foci array passing through a 4 X 4 confocal pinhole array is tilted with a periscope. The tilted array of Raman scattering signals is dispersed by an imaging spectrograph onto a CCD detector, giving 16 independent Raman spectra formed as 16 bands with different heights on the sensor. Use of a state-of-theart imaging spectrograph enables high-precision wavenumber duplicability of the 16 spectra. This high duplicability makes the simultaneously obtained spectra endurable for multivariate spectral analyses, which is demonstrated by a singular value decomposition analysis for Raman spectra of liquid indene. Although the present implementation attains only 16 measurement points, the number of points can be extended to larger than 100 without any technical leaps. Limit of patallelization depends on the interval of measurement points as Well as the performance of the optical system. Criteria for finding the maximum feasible number are discussed.