Browsing by Author "Tanaka, Keiichi"

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Fourier transform microwave spectroscopy of the SiCl+ ion
(2018-03-01)
Tanaka, Keiichi
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Harada, Kensuke
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Cabezas, Carlos
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Endo, Yasuki
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應用化學系
Fourier transform microwave spectra for the J=1 <- 0 and 2 <- 1 rotational transitions of the SiCl+ ion were observed for two isotopologues (Cl-35 and Cl-37) in the ground and the first excited vibrational states of the ground (1)Sigma(+) electronic state. Thanks to the high resolution of the FTMW spectrometer, hyperfine structures due to the quadrupole moment of the chlorine nucleus and the nuclear spin-rotation interaction were fully resolved. The observed FTMW spectra were combined with previously reported MMW and diode laser spectra in an analysis to determine the mass-independent Dunham coefficients U-k,U-l as well as a mass scaling parameter Delta(Cl)(01) = -0.856(30). The equilibrium bond length of SiCl+ determined is r(e) = 1.9439729(10) angstrom and the nuclear quadrupole coupling constant of (SiCl+)-Cl-35 is eQq(e) = -11.8788(23) MHz. (C) 2017 Elsevier Inc. All rights reserved.
Fourier-transform microwave spectroscopy of the H-2-HCN complex
(2012-12-03)
Ishiguro, Masazumi
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Harada, Kensuke
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Tanaka, Keiichi
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Tanaka, Takehiko
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Sumiyoshi, Yoshihiro
Fourier-transform microwave spectroscopy was applied to observe the J = 1-0 rotational transition of the H-2-HCN complex for both the ortho-and para-H-2 species to obtain improved molecular constants by an analysis combined with the millimeter-wave data. It was confirmed that the para-and ortho-H-2 species have different configurations: namely H-2 is attached to the H end of HCN in the former, while to the N end in the latter. For the ortho-H-2 species, the hyperfine splitting due to the magnetic interaction between the hydrogen nuclei was observed to give the nuclear spin-spin coupling constant d(H) = 54.6(38) kHz. (C) 2012 Elsevier B.V. All rights reserved.
Infrared absorption of trans-1-chloromethylallyl and trans-1-methylallyl radicals produced in photochemical reactions of trans-1,3-butadiene and Cl-2 in solid para-hydrogen
(2012-08-28)
Bahou, Mohammed
;
Wu, Jen-Yu
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Tanaka, Keiichi
;
Lee, Yuan-Pern
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應用化學系
The reactions of chlorine and hydrogen atoms with trans-1,3-butadiene in solid para-hydrogen (p-H-2) were investigated with infrared (IR) absorption spectra. When a p-H-2 matrix containing Cl-2 and trans-1,3-butadiene was irradiated with ultraviolet light at 365 nm, intense lines at 650.3, 809.0, 962.2, 1240.6 cm(-1), and several weaker ones due to the trans-1-chloromethylallyl radical, center dot(CH2CHCH)CH2Cl, appeared. Observed wavenumbers and relative intensities agree with the anharmonic vibrational wavenumbers and IR intensities predicted with the B3PW91/6-311++g(2d,2p) method. That the Cl atom adds primarily to the terminal carbon atom of trans-1,3-butadiene is in agreement with the path of minimum energy predicted theoretically, but in contrast to the reaction of Cl + propene in solid p-H-2 [J. Amicangelo and Y.-P. Lee, J. Phys. Chem. Lett. 1, 2956 (2010)] in which the addition of Cl to the central C atom is favored, likely through steric effects in a p-H-2 matrix. A second set of lines, intense at 781.6, 957.9, 1433.6, 2968.8, 3023.5, 3107.3 cm(-1), were observed when the UV-irradiated Cl-2/trans-1,3-butadiene/p-H-2 matrix was further irradiated with IR light from a SiC source. These lines are assigned to the trans-1-methylallyl radical, center dot(CH2CHCH)CH3, produced from reaction of 1,3-butadiene with a H atom resulted from the reaction of Cl atoms with solid p-H-2 exposed to IR radiation. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745075]
Ortho-Para Mixing Hyperfine Interaction in the H2O+ Ion and Nuclear Spin Equilibration
(2013-10-03)
Tanaka, Keiichi
;
Harada, Kensuke
;
Oka, Takeshi
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應用化學系
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Department of Applied Chemistry
The ortho to para conversion of water ion, H2O+, due to the interaction between the magnetic moments of the unpaired electron and protons has been theoretically studied to calculate the spontaneous emission lifetime between the ortho- and para-levels. The electron spin nuclear spin interaction term, T-ab(S-a Delta I-b + S-b Delta I-a) mixes ortho (I = 1) and para (I = 0) levels to cause the "forbidden" ortho to para vertical bar Delta I vertical bar = 1 transition. The mixing term with T-ab = 72.0 MHz is 4 orders of magnitude higher for H2O+ than for its neutral counterpart H2O where the magnetic field interacting with proton spins is by molecular rotation rather than the free electron. The resultant 10(8) increase of ortho to para conversion rate possibly makes the effect of conversion in H2O+ measurable in laboratories and possibly explains the anomalous ortho to para ratio recently reported by Herschel heterodyne instrument for the far-infrared (HIFI) observation. Results of our calculations show that the ortho <-> para mixings involving near-degenerate ortho and para levels are high (similar to 10(-3)), but they tend to occur at high energy levels, similar to 300 K. Because of the rapid spontaneous emission, such high levels are not populated in diffuse clouds unless the radiative temperature of the environment is very high. The low-lying 1(01) (para) and 1(11) (ortho) levels of H2O+ are mixed by similar to 10(-4) making the spontaneous emission lifetime for the para 1(01) -> ortho 0(00) transition 520 years and 5200 years depending on the F value of the hyperfine structure. Thus the ortho <-> para conversion due to the unpaired electron is not likely to seriously affect thermalization of interstellar H2O+ unless either the radiative temperature is very high or number density of the cloud is very low.