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Kensuke Harada Last modified date:2018.06.23

Lecturer / Quantum Chemistry II
Department of Chemistry
Faculty of Sciences


Graduate School
Undergraduate School
Other Organization


E-Mail
Homepage
133.5.167.83
Home page of the Quantum Chemistry Laboratory II .
Phone
092-802-4121
Fax
092-802-4121
Academic Degree
Doctor of Science
Field of Specialization
Molecular Spectroscopy
Outline Activities
Determination of the intermolecular potential between H2 and other molecules is important to understand quantum effects in solid hydrogen. We are measureing internal rotation transitions of H2-containing molecular complexes to determine molecular structures and intermolecular potentials of these complexes. In 2014-2015, we have observed (ortho)H2-H2O and (ortho)H2-D2O complexes and determined intermolecular bond lengths and intermolecular stretching force constants for several internal rotation states. Fourier transform microwave spectra of (ortho)H2-H2O, (ortho)H2-D2O, (para)D2-H2O and (para)D2-D2O have been measured in the joint research project of Kyushu University and Shizuoka University. The result of the joint research has been published in Chem. Phys. Lett., 605-606, 67-70(2014). In the ground internal rotation state, the H2 part is rotating almost freely in the plane with a intermolecular axis and H2 is attached to the oxigen atom of H2O. On the other hand, in the excited state, where the H2 part is rotating around the intermolecular axis, the configuration of the H2O part changes drastically from that in the ground state.
Determination of the intermolecular potential between He and other molecules is important to understand superfluidity in liquid He. We are measureing internal rotation transitions of He-containing molecular complexes to determine intermolecular potentials of these complexes. In 2016-2017, the energy levels of the He-HCN and He-DCN complexes near the dissociation limit have been observed by millimeter wave spectroscopy. Several levels are bound even above the dissociation limit. Energies and life time of several quasi-bound levels are predicted for these complexes. The j=3-2 internal rotation band of Ar-HCN and the j=2-1 internal rotation bands of Ar-DCN have been measured by millimeter wave spectroscopy.
The rotational and tunneling rotation transitions of the vinyl radical generated by UV laser photolysis have been measured by millimeterwave spectroscopy. In HDCCH radical, the tunneling motion is hindered and the spectrum of the cis-HDCCH isomer has been measured. In the D2CCD radical, the large ortho-para mixing interaction has been detected.
The millimeter wave spectroscopy in the vibrational excited state of the FeCO radical was published in J. Chem. Phys, 143, 014303, (2015). The millimeter wave spectroscopy of the SiCl+ ion was published in Chem. Phys. Lett., 651, 168 (2016). The hyperfine structure of the SiCl+ ion was observed by FTMW spectroscopy and published in J. Mol. Spectrosc. 345, 39-45 (2018). The millimeterwave confocal multipass optical system have been reported in Bunko-kenkyu, 65-4, 210-213 (2016).
Research
Research Interests
  • Intermolecular Potential of the weakly bound molecular complexes
    keyword : Molecular complexes, Intermolecular potential, Millimeterwave spectroscopy, He-HCN, He-DCN, H2-HCN, H2-H2O, Ar-HCN, Ar-DCN
    1998.04Determination of the intermolecular potential energy surface of a He-containing molecular cluster is important to understand intermolecular interaction in quantum superfluid He droplet. We have observed intermolecular stretching and internal rotation bands of He-HCN, He-DCN by direct absorption millimeter wave spectroscopy using a high sensitivity multi-reflection millimeter wave cell combined with the pulsed supersonic jet technique. The intermolecular potential energy surface of He-HCN was determined by fitting the observed transitions. Many unidentified lines observed with high stagnation pressure may be due to the internal rotation bands of (He)2-HCN or (He)3-HCN. The pure rotational transitions and HCN internal rotation transitions of the H2-HCN complex have been observed. The para and ortho hydrogen are bound to the hydrogen and nitrogen ends of HCN in the ground internal rotation states. The rotational transitions in the ground and internal rotation excited states of the H2-H2O complex have been observed with millimeter wave spectroscopy..
  • Molecular spectroscopy of the reaction intermediates.
    keyword : Reaction intermediates, Millimeterwave spectroscopy, vinyl, vinyl-d, vinyl-d3, FeCO, CoCO, FeNO, CoNO, Photolysis, SiCl+, OCS+
    2000.04The multi-reflection millimeter wave jet cell combined with the UV laser photolysis is an efficient tool for the detection of the reaction intermediate. We have observed vinyl, vinyl-d(H2CCD, HDCCH), vinyl-d3(D2CCD), FeCO, FeNO, CoCO, and CoNO radicals using this technique. The tunneling splitting and the barrier hight of the proton tunneling of the vinyl radical have been determined by the analysis of the observed tunneling rotation transitions. The hyperfine interaction between the ortho and para levels have been determined. The microwave spectra of the transition metal mono-nitrosyl were observed for the first time. We are now developing a millimeterwave resonator for the sensitive detection of reaction intermediates..
  • High resolution Fourier transform diode laser absorption spectroscopy of radicals and ions.
    keyword : Radical, ion, N2+, Fourier transform spectroscopy, Absorption spectroscopy
    2012.04 The high resolution emmision spectrum of the A-X band of the ClCN+ radical ion produced by the Penning ionization of ClCN has been measured with a Fourier transform spectrometer. The origin band of the A-X system of ClCN+ has been assigned and analysed. The molecular structure as been determined precisely. .
Academic Activities
Books
1. K. Tanaka, K. Harada, and K. M. T. Yamada, THz and submillimeter-wave spectroscopy of molecular complexes., John Wiley & Sons, Ltd., in "HANDBOOK OF HIGHRESOLUTION SPECTROSCOPIES", edited
by M. Quack and F. Merkt, 44 pages, 2011.08.
Reports
1. K. Tanaka, K. Harada, and K. M. T. Yamada, THz and Submillimeter-wave Spectroscopy of Molecular Complexes., "HANDBOOK OF HIGHRESOLUTION SPECTROSCOPIES", John Wiley & Sons, Ltd. , 2009.12.
2. Intermolecular Interactions in Molecular clusters containing Helium and Hydrogen..
Papers
1. Keiichi Tanaka, Kensuke Harada, Carlos Cabezas, Yasuki Endo, Fourier transform microwave spectroscopy of the SiCl+ ion, J. Mol. Spectrosc., 10.1016/j.jms.2017.12.001, 345, 39-45, 2018.01, Fourier transform microwave spectra for the J = 1-0 and 2-1 rotational transitions of the SiCl+ ion
were observed for two isotopologues (35Cl and 37Cl) in the ground and the first excited vibrational states
of the ground 1Σ+ 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 Uk,l as
well as a mass scaling parameter ΔCl01 = -0.856(30). The equilibrium bond length of SiCl+ determined
is re = 1.9439729(10) Å and the nuclear quadrupole coupling constant of Si35Cl+ is eQqe =
-11.8788(23) MHz..
2. Yoshihiro Nakashima, Kensuke Harada, Keiichi Tanaka, Takehiko Tanaka , High-resolution Fourier transform emission spectroscopy of the band of the OCS+ ion
, J. Chem. Phys. , 10.1063/1.4979300, 146, 144302-1-144302-, 2017.04, High resolution Fourier transform emission spectroscopy of the ˜A2Πi–˜X2Πi band of the OCS+ ion
was performed in the UV region to observe the ν1 (CO stretch) progression bands (v1 = 0 → 2–5)
for both the Ω = 3/2 and 1/2 spin components. Accurate molecular constants including the rotational
constants, B0 = 0.194 765(13) and 0.187 106(13) cm-1, and the spin-orbit interaction constants,
A0 = -381.0(56) and -126.5(56) cm-1, were determined for the ˜X 2Π and ˜A2Π states, respectively,
by the simultaneous analysis of the observed progression bands. The CO bond length (rCO = 1.2810
Å) for the ˜A2Π state, derived from the rotational constant B0 and Franck-Condon factors, is longer
by 0.1756 Å than that (1.1054 Å) for the ˜X 2Π state, while the CS bond length for the ˜A2Π state is
shorter by 0.0905 Å than that for the ˜X2Π state. Pure rotational transition frequencies in the ground
˜X2Π state are predicted, as well as transition frequencies of the ν1 fundamental band, with the present
molecular constants..
3. Kazuki Takeda, Satoshi Masuda, Kensuke Harada, Keiichi Tanaka, Millimeter-wave spectroscopy of the SiCl+ ion, Chem. Phys. Lett., 10.1016/j.cplett.2016.03.008, 651, 168-171, 2016.03, The millimeter-wave spectrum of the SiCl+ ion in the ground and first excited vibrational states was
observed for the two isotopic (35Cl and 37Cl) species. The ion was generated in a free-space absorption
cell by a hollow cathode discharge of SiCl4 diluted with He and discriminated from neutral species by
the magnetic field effect on the absorption lines. The observed millimeter-wave spectrum was combined
with a previously reported diode laser spectrum in an analysis to determine mass-independent Dunham
coefficients as well as the mass scaling parameters. The equilibrium bond length of SiCl+ determined is
re = 1.943 978(2) A˚ ..
4. Keiichi Tanaka, Mitsuhiro Nakamura, Mitsuaki Shirasaka, Kensuke Harada, Takehiko Tanaka, Millimeter-wave spectroscopy of the FeCO radical in the ν 2 and ν 3 vibrationally excited states

, J. Chem. Phys. , 10.1063/1.4923215, 143, 014303-1 -014303-10 , 2015.07, The pure rotational spectra of the FeCO radical in the ν 2 (bending) and ν 3 (Fe-C stretching) vibrational states of the ground
˜X3Σ− electronic state were observed in the millimeter-wave region. The equilibrium rotational and centrifugal distortion constants were determined to be B e = 4374.631(58) MHz and D e = 1.1666 (20) kHz together with the spin-spin coupling constant λ e = 691.89 (37) GHz and spin-rotation coupling constant γ e = − 1079.4 (55) MHz with use of the millimeter-wave results and the ν1 IR data. The equilibrium bond length for Fe-C was derived to be 1.725 Å assuming that for C-O to be 1.159 Å. Since the vibronic symmetry of the excited state of bending vibration is 3Π , the analysis of spectrum in the ν2 state required an effective spin-orbit interaction constant of A2 = 6.0219 (61) GHz together with three parity doubling constants of o2 = 36.168 (10) GHz,
p2 = 85.18 (34) MHz, and q2 = 4.7024 (17) MHz. The effective spin-orbit interaction constant A2 is attributed to the vibronic mixing of the 3Π excited electronic states. The vibronic mixing also cause the parity doubling constants o2 and p2 , but the main contribution to q2 is given by the vibrational l-type doubling..
5. Kensuke Harada, Keiichi Tanaka, Hirofumi Kubota, Toshiaki Okabayashi, Fourier-Transform Microwave Spectroscopy of the H2-H2O Complex.

, Chem. Phys. Lett., accepted, 2014.08, Fourier-transform microwave spectroscopy was applied to observe the J=1-0 rotational transition of the ortho-H2-H2O complex and isotopologues in the ground Σ0 state (H2 in the jH2 =1 state and H2O in the ground 000 state) to obtain precise molecular constants. Observed spectra were split into three hyperfine components, confirming the complexes are the ortho-H2/para-D2 species. The determined nuclear spin-spin coupling constant indicates H2 is rotating almost freely in the complex; the Σ0 state is nearly of jH2=1 and kH2=0. For the ortho-H2 species, the nuclear spin-rotation coupling constant was also determined.
.
6. Keiichi Tanaka, Kensuke Harada, Takeshi Oka, Ortho–Para Mixing Hyperfine Interaction in the H2O+ Ion and Nuclear Spin Equilibration.

, J. Phys. Chem. A, 117, 9584-9592, 2013.10, 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, Tab(SaIb + SbIa) mixes ortho (I = 1) and
para (I = 0) levels to cause the “forbidden” ortho to para |!I| = 1
transition. The mixing term with Tab = 72.0 MHz is 4 orders of
magnitude higher for H2O+ than for its neutral counterpart
H2O where the magnetic !eld interacting with proton spins is
by molecular rotation rather than the free electron. The resultant 108 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 ("10−3),
but they tend to occur at high energy levels, "300 K. Because of the rapid spontaneous emission, such high levels are not
populated in di"use clouds unless the radiative temperature of the environment is very high. The low-lying 101 (para) and 111
(ortho) levels of H2O+ are mixed by "10−4 making the spontaneous emission lifetime for the para 101 " ortho 000 transition
520 years and 5200 years depending on the F value of the hyper!ne structure. Thus the ortho ! para conversion due to the
unpaired electron is not likely to seriously a"ect thermalization of interstellar H2O+ unless either the radiative temperature is very
high or number density of the cloud is very low..
7. Masazumi Ishiguro, Kensuke Harada, Keiichi Tanaka, Takehiko Tanaka, Yoshihiro Sumiyoshi, Yasuki Endo, Fourier-Transform Microwave Spectroscopy of the H2-HCN Complex.

, Chem. Phys. Lett., 554, 33-36, 2012.12, Fourier-transform microwave spectroscopy was applied to observe the J = 1-0 rotational transition of the H2-HCN complex for both the ortho- and para-H2 species to obtain improved molecular constants by an analysis combined with the millimeter-wave data. It was confirmed that the para- and ortho-H2 species have different configurations: namely H2 is attached to the H end of HCN in the former, while to the N end in the latter. For the ortho-H2 species, the hyperfine splitting due to the magnetic interaction between the hydrogen nuclei was observed to give the nuclear spin-spin coupling constant dH = 54.6(38) kHz..
8. K. Tanaka, K. Harada, and K. M. T. Yamada, THz and submillimeter-wave spectroscopy of molecular complexes., in "HANDBOOK OF HIGHRESOLUTION SPECTROSCOPIES", edited by M. Quack and F. Merkt, John Wiley & Sons, Ltd., 44 pages, 2011.08.
9. Masato Hayashi, Kensuke Harada, Richard Lavrich, Takehiko Tanaka, and Keiichi Tanaka, Millimeter-wave spectroscopy of H2C=CD: Tunneling splitting
and ortho-para mixing interaction, J. Chem. Phys. , 133, 1 (2010)., 2010.11.
10. K. Tanaka, M. Hayashi, M. Ohtsuki, K. Harada, and T. Tanaka, Millimetre-wave spectroscopy of deuterated vinyl radicals, observation of the ortho–para
mixing interaction and prediction of fast ortho–para conversion rates, Mol. Phys., DOI: 10.1080/00268971003685764, in press, 2010.11.
11. K. Tanaka, M. Hayashi, M. Ohtsuki, K. Harada, and T. Tanaka, Ortho-para mixing interaction in the vinyl radical detected by millimeter-wave spectroscopy., J. Chem. Phys., 131, 111101(1-4), 2009.10.
12. A. Sakamoto, M. Hayashi, K. Harada, T. Tanaka, and K. Tanaka, Millimeterwave Spectroscopy of CoNO Produced by UV Laser Photolysis of Co(CO)3NO., J. Chem. Phys. , 129, 134303(1-7), 2008.10.
13. K. Tanaka, M. Toshimitsu, K. Harada, and T. Tanaka, Determination of the proton tunneling splitting of the vinyl radical in the ground state by millimeter-wave spectroscopy combined with supersonic jet expansion and ultraviolet photolysis.
, J. Chem. Phys., 10.1063/1.1642583, 120, 8, 3604-3618, Vol.120, 3604-3618, 2004.02.
14. Kensuke Harada, Keiichi Tanaka, Takehiko Tanaka, Shinkoh Nanbu, and Mutsumi Aoyagi, Millimeter-wave Spectroscopy of the Internal-rotation Band of the He-HCN Complex
and the Intermolecular Potential Energy Surface., J. Chem. Phys., Vol.117, 7041-7050, 2002.10.
15. K. Harada and T. Tanaka,, Near-Infrared Diode Laser Absorption Spectroscopy of the (2, 0) Band of the A2Pu-X2Sg+ System of the N2+ Ion Generated in a Supersonic Jet Expansion., Chem. Phys. Lett., 10.1016/0009-2614(94)00880-9, 227, 6, 651-655, Vol.227, 651-655 (1994)., 1994.09.
16. K. Harada, S. Akao, K. Miyachi, K. Tanaka, and T. Tanaka,, CO2 Laser Stark Spectroscopy of the n4 Band of SiHF3 : The C0 Rotational Constant and Vibrationally Induced Dipole Moment, J. Chem. Phys., 10.1063/1.462444, 96, 1, 5-12, Vol.96, 5-12 (1992)., 1992.01.
17. K. Harada, K. Tanaka, and T. Tanaka,, Observation of Vibrationally Induced Rotational Transitions in the n5 State of CDF3 by CO2 Laser-Microwave Double Resonance Spectroscopy., Chem. Phys. Lett., 10.1016/0009-2614(85)87057-3, 120, 3, 276-279, Vol.120, 276-279 (1985)., 1985.10.
18. K. Harada, M. Hatanaka, A. Inayoshi, K. Tanaka, and T. Tanaka,, CO2 Laser-Microwave Double Resonance and Stark Lamb-dip Spectroscopy of the n5 Band of CDF3., J. Mol. Spectrosc., 10.1016/0022-2852(84)90183-8, 108, 2, 249-263, Vol.108, 249-263 (1984)., 1984.12.
Presentations
1. Millimeter-wave spectroscopy of the j =3-2 internal rotation band of the Ar-HCN complex
, [URL].
2. Kensuke Harada and Keiichi Tanaka, MILLIMETER-WAVE SPECTROSCOPY OF He-HCN AND He-DCN: ENERGY LEVELS NEAR THE DISSOCIATION LIMIT., The 72nd International Symposium on Molecular Spectroscopy, 2017.06, [URL], The He-HCN complex is a weakly bound complex with binding energy of about 9 cm-1. We have measured the j=1 ← 0 internal rotation fundamental band of the He-HCN complex by millimeter-wave absorption spectroscopy and reported the potential energy surface (PES) to reproduce the observed transition frequencies.a) In the present study, we have extended the measurement to the j=2 ← 1 internal rotation hot bands of the He-HCN and He-DCN complexes. In the analysis, the upper state of several observed transitions are found to be located above the "dissociation limit" (D0). The rovibtrational levels with e label dissociate to the HCN molecule with j=0 and the He atom (D0), while those with f label, due to the parity conservation, to the HCN molecule with j=1 and the He atom which is higher in energy by about 2.96 cm-1 (2BHCN) than D0. The f levels are bound up to D0 + 2BHCN. The revised PES of He-HCN has a global minimum in the linear He--HCN configuration with a depth of 29.9 cm-1 and has a saddle point at the anti-linear He--NCH configuration with a depth of 20.9 cm-1.
The νs intermolecular stretching first excited state and the j=2 internal rotation second excited state are determined to be located 9.1405 and 9.0530 cm-1 above the ground state and very close to the calculated dissociation limit (D0) of 9.32 cm-1. Life times of several quasi-bound levels (both of e and f labels) and line widths of the related transitions are predicted for He-HCN and He-DCN from the revised PESs.
a). K. Harada, K. Tanaka, T. Tanaka, S. Nanbu, and M. Aoyagi, J. Chem. Phys. 117, 7041 (2002)..
3. Yoshihiro Nakashima, Kensuke Harada, Keiichi Tanaka and Takehiko Tanaka , High-resolution Fourier transform emission spectroscopy of the A2Πi - X2Πi band of the OCS+ ion
, The Asian Workshop on Molecular Spectroscopy, 2017.05, High resolution Fourier transform (FT) emission spectroscopy of the A2Πi - X2Πi band of OCS+ generated by the Penning ionization with metastable He* atom was performed in the 370 - 490 nm UV region at a resolution of 0.03 cm-1. The ν1 (CO stretching) progression bands from the ground vibrational state of A2Πi to the ν1 excited states of X2Πi were observed; for the v1 = 0 ← 2 - 5 bands of the Ω = 3/2 and 1/2 components. The P- and R-branch lines for Ω = 1/2 were resolved by the parity doubling.
Observed ν1 progression bands were analyzed together with the origin bands reported by LIF study to give the accurate molecular constants of OCS+. The spin-orbit interaction constants A0 determined are -381.0(56) and -126.5(56) cm-1, respectively, for the X2Πi and A2Πi states to agree with the previously reported ones. The CO bond length for the A2Πi state is longer by 0.1756 Å than that for the X2Πi state, while the CS bond length by 0.0905 Å shorter, as determined by the observed rotational constants B0 and Franck-Condon factors, implying the excited state has much weaker CO bond than that of the ground state. The large change in the molecular structure between A2Πi and X2Πi causes the prominent ν1 progression bands observed in the present FT emission spectrum..
4. Kensuke Harada and Keiichi Tanaka , Millimeter-wave spectroscopy of He-HCN and He-DCN: Energy levels near the dissociation limit.
, The Asian Workshop on Molecular Spectroscopy, 2017.05, The He-HCN complex is a weakly bound complex. We have observed the the j=1-0 and 2-1 internal rotation and intermolecular stretching bands of He-HCN and He-DCN by millimeter-wave absorption spectroscopy. The upper state of several observed transitions were found to be located above the "dissociation limit" (D0). These levels are bound due to the parity conservation. The potential energy surface (PES) fitted to the observed transitions has a global minimum in the linear He--HCN configuration with a depth of 29.9 cm-1 and has a saddle point at the anti-linear He--NCH configuration. Life times of several quasi-bound levels are predicted for both isotopic species. .
5. Millimeter wave spectroscopy of the j=2-1 band of the Ar-DCN complex, [URL].
6. Millimeter wave spectroscopy of the HDCCH radical
, [URL].
7.
.
8. Keiichi Tanaka, Kensuke Harada, Yoshihiro Sumiyoshi, Masakazu Nakajima, Yasuki Endo, FOURIER-TRANSFORM MICROWAVE AND MILLIMETERWAVE SPECTROSCOPY OF THE H2-HCN MOLECULAR COMPLEX

, The 70th International Symposium on Molecular Spectroscopy, 2015.06, [URL], Fourier-Transform microwave (FTMW) spectroscopy has been applied to observe the J = 1 - 0 rotational transitions of the H2-HCN/DCN complexes containing both the para-H2(IH2=0) and ortho-H2(IH2=1) molecule. Rotational spectra of H2-HCN/DCN up to J = 5 - 4 were also observed in the millimeter-wave (MMW) region below 180 GHz. Observed FTMW lines for H2-HCN/DCN split into hyperfine components due to the nuclear quadrupole interaction of N and D nuclei. For the ortho-H2 species, the hyperfine splitting due to the magnetic interaction between the hydrogen nuclear spin of ortho-H2 part (jH2=1, IH2=1) was also observed, but not for the para-H2 species (jH2=0, IH2=0). From the observed nuclear spin-spin coupling constants of ortho-H2 species,
d = 21.90(47) and 24.66(68) kHz for HCN and DCN complexes, respectively, the average values of = 0.380(8) and 0.439(10) were derived indicating the nearly free rotation of H2 in the complex with jH2 = 1 and kH2 = 0.
The nuclear quadrupole interaction constants due to N and D nuclei show that the HCN/DCN part executes a floppy
motion with a large mean square amplitude of about 29/25 and 33/30 degree in the para and ortho species, respec-
tively. From the observed rotational constants, the center-of-mass distances of H2 and HCN/DCN were derived to be
3.9617(5)/4.00356 (43) A for the ortho species and 4.1589(13)/4.1596 (36) A for the para species. The isotope effect on
rotational constants confirmed the totally different configurations in the ortho and para species: H2 is attached to the H/D
end of HCN/DCN for the para species, while to the N end for the ortho species, as suggested by IR spectroscopy and
theoretical study.

a. M. Ishiguro et al., Chem. Phys. Lett. 554, 33 (2012).
b. M. Ishiguro et al., J. Chem. Phys. 115, 5155 (2001).
.
9. Millimeter-wave Spectroscopy of the HDCCH and D2CCD Radicals.


, [URL].
10. Kensuke Harada, Keiichi Tanaka, Toshifumi Kubota, Toshiaki Okabayashi, FOURIER-TRANSFORM MICROWAVE SPECTROSCOPY OF THE H2-H2O COMPLEX
,
Kensuke Harada,
Keiichi Tanaka
,
Hirofumi Kubota, Toshiaki Okabayashi
, The 23rd International Conference on High Resolution Molecular Spectroscopy, 2014.09, [URL], The H2-H2O complex is a weakly bound complex with two floppy rotors of H2 and H2O [1]. The H2 moiety is sitting on the C2 axis and H2O works as a proton acceptor in the equilibrium configuration (Fig. 1). Due to the nuclear spin statistics, p-H2 (IH2 = 0) has the jH2 =0 internal rotational state, while o-H2 (IH2 =1) the jH2 =1 state. The p- and o-H2 complexes behave as different molecules with different binding energies (D0) of 34 and 54 cm1 [2]. The H2O part also has two nuclear spin states, Fig. 1 H2-H2O complex
p-H2O (IH2O = 0) and o-H2O (IH2O = 1).
The 2 (H2O bending) band of (o)H2-H2O from the lowest internal rotation state (JKaKc = 000 and 101) has been observed by IR spectroscopy [1], but for the p-H2 species no spectral lines were detected. The ground 000 state of o-H2 complex (jH2 =1) split into two sub-levels, 0 and 0, depending on kH2 = 0 or 1 (see Fig. 1), and the 0 state is located by 14 cm-1 higher than the 0 state according to the DVR calculation [2] with the ab initio PES. By IR study [1] in the jet expansion, the spectral lines only from the 0 ground state have been observed.
In the present study, the J =10 rotational transitions of (o)H2-H2O, (o)H2-D2O, (p)D2-H2O, and (p)D2-D2O in the ground 0 state (H2 in jH2 = 1 and H2O in 000 state) have been observed by FTMW [3]. Observed spectra were split into three hyperfine components due to the nuclear spin of o-H2/p-D2 (IH2/D2=1) (Fig. 2). The nuclear spin-spin interaction constants d were determined to be 24.68(100) and 22.26(100) kHz for (o)H2-H2O and (o)H2-D2O, respectively. The average values of , where  is the angle between the H2 bonding axis and the intermolecular axis (Fig. 1), were calculated to be 0.428(17) and 0.386(17) from the observed d constants, indicating that H2 is rotating almost freely in the complex and the 0 ground state is nearly of jH2 =1 and kH2 =0. The nuclear spin-rotation coupling constant was also determined for (o)H2-species. The average center-of-mass distances are calculated to be 3.600 and 3.612 Å for (o)H2-H2O and (o)H2-D2O from the observed rotational constants,
while the distances for the p-D2 substituted species are Fig. 2 J=1-0 transition of (o)H2-H2O
shorter by 0.168 and 0.184 Å than those for the o-H2 species.

References
[1] M. J. Weida and D. J. Nesbitt, J. Chem. Phys. 110, 156 (1999).
[2] A. van der Avoird and D. J. Nesbitt, J. Chem. Phys. 134, 044314 (2011).
[3] K. Harada, K. Tanaka, H. Kubota, and T. Okabayashi, Chem. Phys. Lett. in press (2014).
.
11. Keiichi Tanaka, Masazumi Ishiguro, Kensuke Harada, Yoshihiro Sumiyoshi, M. Nakashima, Yasuki Endo, FOURIER-TRANSFORM MICROWAVE AND MILLIMETERWAVE SPECTROSCOPY OF THE H2-HCN MOLECULAR COMPLEX
, The 23rd International Conference on High Resolution Molecular Spectroscopy, 2014.09, [URL].
12. Kensuke Harada, Yukiya Iwasaki, Thomas Giesen, Keiichi Tanaka, MILLIMETER WAVE SPECTRA OF THE INTERNAL ROTATION EXCITED STATES OF (o)H2-H2O AND (o)H2-D2O
, The 66th International Symposium on Molecular Spectroscopy, 2013.06, [URL], H2-H2O is a weakly bound complex and it has a various states according to the internal rotation for both H2 and H2O moieties.
In our previous study, we have reported the pure rotational transitions of the (o)H2 complex in the ground H2O rotational state, 000(Sigma),
for both H2-H2O and H2-D2O, where (o)H2 (jH2 =1) is rotating perpendicular to the intermolecular axis to give the projection of jH2 to the axis kH2
to be zero (i.e. Sigma state).

In the present study, we have observed the rotational transitions for the 000 (Pi) states in the millimeter-wave region up to 220 GHz,
where the (o)H2 is rotating around the intermolecular axis to give the projection kH2 to be one (i.e. Pi state).
The center of mass bond lengths derived from the observed rotational constants for 000 (Pi) are longer by 5 % than those for 000 (Sigma),
while force constants for the intermolecular stretching for 000 (Pi) derived from centrifugal distortion constants are
smaller by 23 % than those for 000 (Sigma), suggesting the Pi and Sigma substates have quite different structures.

The recent theoretical calculation (Ad.~van~der~Avoid and D.~J.~Nesbit, J.~Chem.~Phys. 134, 044314 (2011).) indicates
that for 000 (Sigma), (o)H2 is bound to the oxygen site of H2O, while for the 000 (Pi) state, (o)H2 to the hydrogen site of H2O,
and the 000 (Sigma) state is by 14 cm-1 more stable than the 000 (Pi) state. Observed molecular constants for 000 (Sigma) and (Pi)
are consistent with the structures given by the theoretical calculation.

~~~~We also observed the rotational spectrum in the 101 (Sigma) and (Pi) states, where Sigma and Pi correspond to the rotation of H2O
perpendicular and parallel to the intermolecular axis and (o)H2 is calculated to be bound to the oxygen site of H2O.
The energy difference between the 101 (Sigma) and (Pi) states will be discussed due to the Criolis interaction between these substates.
.
13. , [URL].
14. Millimeter wave spectroscopy of the ground and internal rotation excited states of the (o)H2-H2O and (o)H2-D2O complexes

.
15. Millimeter wave spectroscopy of the internal rotation excited states of the (o)H2-H2O and (o)H2-D2O complexes


, [URL].
16. Millimeter wave spectroscopy of the (o)H2-D2O complex: Observation of the rotational spectrum in the internal rotation excited state of the (o)H2 part

, [URL].
17. Millimeter wave spectroscopy of the (o)H2-D2O complex: Observation of the rotational spectrum in the internal rotation excited state of the (o)H2 part

, [URL].
18. Intermolecular Potential of He-HCN and H2-HCN. , [URL].
19. Millimeter Wave Spectroscopy of the vdW Transitions of He-HCN Near the Dissociation Limit. , [URL].
20. Millimeter Wave Spectroscopy of the vdW Transitions of He-DCN Near the Dissociation Limit. , [URL].
21. , [URL].
22. , [URL].
23. Spectroscopy and Reaction Dynamics of Reaction Intermediates and Molecular Complexes..
24. , [URL].
25. , [URL].
26. , [URL].
27. Millimeter Wave Spectroscopy of Weakly Bound Molecular Complexes., [URL].
28. , [URL].
29. , [URL].
30. Ortho-para conversion rate of the vinyl radical., [URL].
31. Millimeterwave Spectrum of the Internalrotation Transitions of He-HCN over the Dissociation Limit., [URL].
32. Sensitive detection of the radical species by millimeterwave cavity spectrometer, [URL].
33. Millimeterwave Resonator for the Sensitive Detection of the Radical Species , [URL].
34. Millimeterwave spectroscopy of the radicals and molecular complexes..
35. , [URL].
36. Millimeterwavespectroscopyofmolecularcomplexeswithalowtemperaturejetnozzle., [URL].
37. , [URL].
38. , [URL].
39. , [URL].
40. , [URL].
41. , [URL].
42. , [URL].
43. , [URL].
44. , [URL].
45. , [URL].
46. , [URL].
47. , [URL].
48. , [URL].
Membership in Academic Society
  • The Chemical Society of Japan
  • The Spectroscopical Society of Japan
  • Japan Society of Molecular Science
Awards
  • "Millimeter-wave spectroscopy of deuterated vinyl radicals, observation of the ortho-para mixing interaction
    and predicton of the fast ortho-para conversion rates",
    K. Tanaka, M. Hayashi, M. Ohtsuki, K. Harada, and T. Tanaka,
    Mol. Phys., 108, 2289(2010). (Invited Article)
Educational
Educational Activities
1. Quantum chemistry I
2. Basic theory of the chemical bond
3. Science experiments of undergraduate students
4. Physical Chemistry expariments of the undergraduate students
5. Laboratory works of the graduate student
6. Laboratory works of the undergraduate student
Social
Professional and Outreach Activities
High sensitive detection method using near infrared diode laser absorption spectroscopy.
The joint research project with the Mitsubishi Heavy Industry Co., 1994..