Nobuhiko Kuze

Microwave spectrum, molecular structure, and ab initio calculation of (E)-chloroacetaldehyde oxime

Abstract The microwave spectra of (E)-35ClCH2CHNOH, (E)-37ClCH2CHNOH, (E)-35ClCH2CHNOD, and (E)-37ClCH2CHNOD have been observed in the frequency range from 26.4 to 40.5 GHz. The rotational and centrifugal distortion constants of the four isotopic species in the ground and excited vibrational states were determined. The values of the ΔI( = Ic − Ia − Ib) obtained for the normal (35Cl and 37Cl) and deuterated (35Cl and 37Cl) species in the ground vibrational state were found to be − 16.350(4), − 16.36(4), − 17.06(4), and − 17.07(6) uA2, respectively. The molecular structure of this molecule was determined to be the anticlinal form ( ф 1 :∠ ClCCN = 121.4° , ф 2 :∠ CNOH = 180.0° ), as shown in Fig. 1(a). It was found that ab initio calculation of MP 2 6-31 G ∗∗ level can be used to predict the most stable rotational conformer of (E)-ClCH2CHNOH. The seven structural parameters of the heavy atom skeleton of this molecule were fitted to the eight rotational constants (B and C) of the four isotopic species. The obtained structural parameters (r0) are almost the same as those (rα) obtained previously by a gas-phase electron diffraction study (K. Iijima, T. Miwa, T. Sakaizumi, O. Ohashi, J. Mol. Struct. 352/353 (1995) 161), within the errors. The r(CN and ∠CCN obtained for (E)-ClCH2CHNOH are slightly shorter and drastically narrower than those of (Z)-ClCH2CHNOH. The trend is consistent with those of CH3CHNOH and CH3CH2CHNOH.

MOLECULAR STRUCTURE AND PROPERTIES OF SOME LINEAR MOLECULES : A STUDY OF POST HARTREE-FOCK AND DENSITY FUNCTIONAL THEORY

Abstract We have chosen a few linear molecules [NCCCX, X=H, F, Cl, Br; FCCH, FCCF, ClCCCl], containing electronegative atoms to study the structure and properties of these molecules by using a higher level of DFT and ab initio methods. The molecular geometries were optimized employing the atomic basis sets 6-311++G(2d,2p), 6-311++G(3df,3pd) in BLYP, B3LYP, BP86 level of theory of DFT and 6-13G* basis set at MP2 level of theory in the ab initio method. The optimized structural parameters and other properties of the molecules obtained by the post-Hartree–Fock and DFT methods are discussed with experimental values. Density functional theory parameters chemical hardness and chemical potential were calculated employing the atomic basis set 6-13G* at the MP2 level of theory in the ab initio method. These parameters were discussed in relation to the electronegativity of the atoms.

Molecular Structure and Internal Rotation of CF3 Group of Methyl Trifluoroacetate: Gas Electron Diffraction, Microwave Spectroscopy, and Quantum Chemical Calculation Studies

The molecular structure of methyl trifluoroacetate (CF3COOCH3) has been determined by gas electron diffraction (GED), microwave spectroscopy (MW), and quantum chemical calculations (QC). QC study provides the optimized geometries and force constants of the molecule. They were used to estimate the structural model for GED study and to calculate the vibrational corrections for GED and MW data. In addition, potential energy curves for the internal rotations of CF3 and CH3 groups have been calculated for anti (dihedral angle of α(CCOC) is 180°) and syn (α(CCOC) = 0°) conformers of methyl trifluoroacetate. Both the GED and MW data revealed the existence of the anti conformer. Molecular constants determined by MW are A0 = 3613.4(3) MHz, B0 = 1521.146(8) MHz, C0 = 1332.264(9) MHz, ΔJ = 0.09(2) kHz, and ΔJK = 0.23(6) kHz. The GED data were well-reproduced by the analysis in which a large-amplitude motion of the CF3 group was taken into account. The barrier of the internal rotation of the CF3 group was determined to be V3 = 2.3(4) kJ mol(-1), where V3 is the potential coefficient of the assumed potential function, V(ϕ) = (V3/2)(1 - cos 3ϕ), and ϕ is a rotational angle for the CF3 group. The values of geometrical parameters (re structure) of the anti conformer of CF3COOCH3 are r((O═)C-O) = 1.326(6) Å, r(O-CH3) = 1.421(4) Å, r(C-H(in-plane)) = 1.083(14) Å, r(C-H(out-of-plane)) = 1.087(14) Å, r(C═O) = 1.190(7) Å, r(C-C) = 1.533(4) Å, r(C-F(in-plane)) = 1.319(4) Å, r(C-F(out-of-plane)) = 1.320(6) Å, ∠COC = 116.3(5)°, ∠OCH(in-plane) = 105.2° (fixed), ∠OCH(out-of-plane) = 110.0° (fixed), ∠O═CC = 123.7° (fixed), ∠O-CC = 111.2(5)°, ∠OCO = 125.2(5)°, ∠CCF = 110.1(3)°, and OCCF (out-of-plane dihedral angles) = ± 121.5(1)°. Numbers in parentheses are three times the standard deviations of the data fit.

Radio Search for H2CCC toward HD 183143 as a Candidate for a Diffuse Interstellar Band Carrier

To clarify the authenticity of a recently proposed identification of H2CCC (linear-C3H2) as a diffuse interstellar band (DIB) carrier, we searched for the rotational transition of H2CCC at a frequency of 103 GHz toward HD 183143 using the 45 m telescope at the Nobeyama Radio Observatory. Although rms noise levels of 32 mK in the antenna temperature were achieved, detection of H2CCC was unsuccessful, producing a 3σ upper limit corresponding to a column density of 2.0 × 1013 cm–2. The upper limit indicates that the contribution of H2CCC to the DIB at 5450 A is less than 1/25; thus, it is unlikely that the laboratory bands of the B 1 B 1-X 1 A 1 transition of H2CCC and the DIBs at 5450 A (and also 4881 A) toward HD 183143 are related.

Microwave spectroscopic and ab initio studies of pyrolysis products of 2-nitrosopropene (syn form) and its pyrolysis mechanism

Abstract The pyrolysis products of CH2C(CH3)NO (syn form) have been determined by microwave spectroscopy. The pyrolysis products of CH2C(CH3)NO (syn form) and its 15N isotopic species were found to be CH2O, CH3CN, and CH3C15N. The produce of formaldehyde and methyl cyanide suggests that the CC and NO double bonds of CH2C(CH3)NO (syn form) were broken. To explain the generation of the two molecules, a four-membered ring molecule (9) as an intermediate, is proposed. The four-membered ring molecule as an intermediate is also supported by ab initio MO calculation. Applying the pyrolysis mechanism obtained for 2-nitrosopropene (syn form) to that of 1,1,2-trichloronitrosoethane, one of its complicated pyrolysis mechanisms was explained. The rotational constants and geometrical parameters of two intermediates, 9 and CH2CClNO (13), were obtained by ab initio MO calculation (MP2/6-31G**) to predict their microwave spectra.

PCI effects and the gradual formation of Rydberg series due to photoelectron recapture, in the Auger satellite lines upon Xe 4d?15/2 photoionization

The Xe (N5O2,3O2,3) Auger electron spectra originating from 4d−15/2 inner-shell photoionization were measured, with photon energy tuned close to the ionization threshold. As the photon energy approaches the threshold from above the 4d−15/2 photoionization threshold, Rydberg series structures are formed within the Auger electron peak by the recapture of the photoelectron into high-lying ion orbitals. They emerge in the tail on the higher energy side of the post–collision interaction (PCI) profile of the Auger electron. Discrete Rydberg peaks replace the continuous PCI tail and gradually form a series with intensity distribution emulating the intensity profile of the continuous tail. Structures due to the Xe+5p4(1S0, 1D2, 3P2,1,0) ml series were observed and assigned.

Mass and microwave spectroscopic studies of the pyrolysates and pyrolysis mechanism of 1-chloro-2-isocyanatoethane and 1-chloro-2-isothiocyanatoethane

Abstract The pyrolysates of ClCH 2 CH 2 NCO and ClCH 2 CH 2 NCS were investigated by pyrolysis-mass spectrometry and microwave spectroscopy (Py-MS/MW) at 100–900°C. In the mass spectrum of the pyrolysate of ClCH 2 CH 2 NCO a characteristic ion is seen at m/z 69, while in that of ClCH 2 CH 2 NCS ions at m/z 59, 62, 64, and 85 are observed. The identification by MW revealed that the ion at m/z 69 is the molecular ion of vinyl isocyanate, while the ion at m/z 59 is that of isothiocyanic acid, at m/z 62 and 64 are those of vinyl chloride, and at m/z 85 is that of vinyl isothiocyanate. In spite of the similarity of the two compounds, it was found that the pyrolysis mechanism of ClCH 2 CH 2 NCS was different from that of ClCH 2 CH 2 NCO. The generation of vinyl chloride and isothiocyanic acid from ClCH 2 CH 2 NCS suggests that the CN single bond of ClCH 2 CH 2 NCS may be weaker than that of ClCH 2 CH 2 NCO.

Laboratory Detection of a Linear Carbon Chain Alcohol: HC4OH and Its Deuterated Species

The rotational spectra of HC4OH and its deuterated species have been detected in the 17-39 GHz region by microwave spectroscopy. The spectra were generated after pyrolysis of 2-butynol at 830°C; a deuteration reaction to produce DC4OH and HC4OD was caused by mixing the 2-butynol with deuterated water vapor. The rotational constants B and C were precisely determined for HC4OH and the rotational constant (B + C)/2 was determined for DC4OH and for HC4OD. With these rotational constants, the entire radio spectrum of HC4OH can be accurately estimated to better than 0.42 MHz accuracy at frequencies up to 51.1 GHz. These transition frequencies should be of great use for astronomical identification of this molecule.

Probing electron correlation through radiative lifetime measurements upon inner-valence photoionization of Ne and Ar

This work demonstrates that electron correlation can have a strong effect on the radiative lifetime of atoms. We report measurements of the radiative lifetimes of inner-valence hole states, the 3s3p6 2S1/2 state of Ar+ and the 2s2p6 2S1/2 state of Ne+ by using the time-correlated single photon counting technique combined with photoionization by synchrotron radiation. Theoretical calculations utilizing the multi-configuration Dirac–Fock method agreed well with the experimental results. In particular, the radiative lifetime was found to depend very sensitively on the mixing of valence excited state configurations. While the Ne+ 2s2p6 2S1/2 state only has relatively weak inter-shell correlation, Ar+ 3s3p6 2S1/2 state has strong intra-shell correlation within the M-shell. This intra-shell correlation enhances configuration mixing and causes the radiative lifetime of the Ar+ 3s3p6 2S1/2 state to become very much longer than that of the Ne+ 2s2p6 2S1/2 state.

A SEARCH FOR THE HOCO RADICAL IN THE MASSIVE STAR-FORMING REGION Sgr B2(M)

Rin Abe, Ayane Miyazaki, Takahiro Oyama, Mitsunori Araki, Shuro Takano, Nobuhiko Kuze, Yoshihiro Sumiyoshi, Koichi Tsukiyama, Yasuki Endo 1 Department of Chemistry, Tokyo University of Science, Japan 2 Department of Physics, College of Engineering, Nihon University, Japan 3 Department of Materials and Life Science, Sophia University, Japan 4 Division of Pure and Applied Science, Graduated School of Science and Technology, Gunma University, Japan 5 Department of Applied Chemistry, National Chiao Tung University, Taiwan