Hideta Habara

Fourier transform millimeter-wave spectroscopy of chlorocarbene (HCCl)

The 101–000 and 202–101 rotational transitions of HC35Cl and HC37Cl in the X 1A′ ground vibronic state have been observed with a Fourier transform millimeter-wave spectrometer. The HCCl molecule is produced by discharging a gaseous sample of CH2Cl2 diluted in Ar with a pulsed discharge nozzle. The effective rotational constant (B+C)/2, the centrifugal distortion constant ΔJ, the nuclear quadrupole interaction constants, and the nuclear-spin rotation interaction constant are determined for each isotopic species. The nuclear-spin rotation interaction is found to make a significant contribution to the hyperfine structure of this molecule, which originates from the relatively low-lying electronic excited state. The nuclear quadrupole interaction tensor is highly asymmetric, indicating a significant π character of the C–Cl bond. This can be interpreted in terms of the backdonation of π electrons from the chlorine atom to the carbon atom.

Fourier transform millimeter-wave spectroscopy of the HCS radical in the 2A′ ground electronic state

The 101–000 rotational transition of the HCS radical in the X 2A′ ground electronic state has been observed with a Fourier transform millimeter-wave spectrometer in combination with a pulsed discharge nozzle. The radical is produced by discharging a mixture of CH4 and H2S diluted in Ar. Six fine and hyperfine components are detected, and the effective rotational constant, spin–rotation interaction constant, and hyperfine interaction constants are determined accurately. The Fermi contact term of the hydrogen nucleus is found to be much smaller than that for the isovalent radical, HCO, indicating that the HCS radical is more close to a linear structure than the HCO radical.

Submillimeter-wave measurements of the pressure broadening of BrO

The N2 and O2 pressure broadening coefficients of the J=23.5←22.5 and J=25.5←24.5 rotational transitions in the ground vibronic state X2Π3/2 of 81BrO at 624.768 and 650.178GHz have been independently measured at Ibaraki University and Jet Propulsion Laboratory. These lines are expected to be monitored by the superconducting submillimeter-wave limb emission sounder in the Japanese Experiment Module on the International Space Station (JEM/SMILES) as well as the earth observing system microwave limb sounder (EOS-MLS). This work provides temperature-dependent pressure broadening parameters of BrO needed by the space station and satellite based observations. The BrO pressure broadening coefficients and their 1σ uncertainties are: γ0(N2)=3.24±0.05MHz/Torr and γ0(O2)=2.33±0.06MHz/Torr for the 624.768GHz transition at room temperature (296K). For the 650.178GHz line, the results are: γ0(N2)=3.20±0.07MHz/Torr and γ0(O2)=2.41±0.06MHz/Torr. The temperature dependence exponents and their 1σ error are determined to be: n(N2)=−0.76±0.05 and n(O2)=−0.93±0.07 for the 624.768GHz transition, and n(N2)=−0.84±0.07 and n(O2)=−0.70±0.07 for the 650.178GHz transition.

Microwave spectrum and molecular structure of the HSC radical

The HSC radical, that is a geometrical isomer of the HCS radical, has been identified and characterized by microwave spectroscopy. The HSC radical has been produced in a discharge plasma of a gaseous mixture of H2S and CO, and its rotational spectral lines are observed with a source-modulation spectrometer and a Fourier-transform millimeter-wave spectrometer. The spectrum of the deuterated species, DSC, has also been measured with a source-modulation spectrometer. Rotational constants, centrifugal distortion constants, and spin–rotation interaction constants with their centrifugal distortion corrections for HSC and DSC are determined from the observed transition frequencies by a least-squares method. Furthermore hyperfine interaction constants of the hydrogen nucleus are also determined for HSC. The Fermi contact term of the hydrogen nucleus takes a large positive value, 288.845±0.185 MHz, which indicates that the HSC radical is a σ radical (2A′) in the ground electronic state. The harmonic force field is...

Submillimeter-wave spectra of HCS and DCS

The a-type R-branch K−1=0 rotational transitions of the HCS and DCS radicals have been measured in the frequency range of 161 to 644 GHz using source modulation spectrometers. For DCS, the seven fine and hyperfine components of the 101–000 rotational transition are also measured at 35 GHz using a Fourier transform millimeter-wave spectrometer. The spectra are found to be perturbed by the K−1=1 state through the off-diagonal spin–rotation interaction (eab+eba)(NaSb+SbNa+NbSa+SaNb). In particular for DCS, strong perturbations are observed. The rotational constants, A, B+C, and B−C, of DCS are determined through an analysis of the perturbation. The r0 structure of HCS has been determined as follows: r0(CH)=1.079(3) A, r0(CS)=1.562 28(3) A, and α0(HCS)=132.8(3)°. The quasilinearity parameter, γ0, is evaluated to be 0.80 for DCS, indicating that HCS is not a simple bent molecule.

Microwave spectrum and molecular structure of the H2NS radical

The rotational spectral lines of the H2NS and D2NS radicals in the X2B1 electronic ground state are observed with a source-modulation microwave spectrometer and a Fourier-transform microwave spectrometer. Molecular constants including hyperfine interaction constants are determined for H2NS and D2NS by a least-squares method. By using the obtained centrifugal distortion constants and inertial defects, the harmonic force field is evaluated, and the frequency of the ν4 vibrational mode (out of plane) is calculated to be 325 cm−1. This value is much smaller than that of the related molecule H2CS, indicating a floppy motion along the out-of-plane mode. The zero-point vibrational average structure was determined as follows; rz(N–H)=1.000(5) A, rz(N–S)=1.6398(13) A, and ∠z(HNH)=118.9(7)°, where the numbers in parentheses represent three times the standard deviation.

Submillimetre-wave spectrum of NCS

Rotational transitions of the NCS radical have been observed in the submillimetre-wave region up to 645 GHz by using a backward-wave oscillator based spectrometer. In addition to the ground vibronic state lines, the transitions have been identified for all the four states in the v 2  = 1 state. The ‘parity splittings’ for the Δ levels of the (010) excited bending vibrational state were found to be much larger than expected. The standard vibronic Hamiltonian set up for the four sub-states failed to explain the excited state lines for these sub-states together. In this investigation, the lower two components, 2Δ5/2 and μ 2Σ, and the upper two components, 2Δ3/2 and κ 2Σ, were fitted separately assuming different sets of molecular constants. The lines in the ground vibronic state, , of 14 N 12 C 34S were observed in natural abundance. The r 0 structure of this radical was calculated by using the rotational constants for the normal species and that for the 34S species.

Fourier transform microwave spectroscopy of the CH2CP(X̃ 2B1) radical

The hyperfine resolved rotational spectrum of the CH2CP radical in the X 2B1 ground electronic state has been observed for the first time using a Fourier transform microwave spectrometer in combination with a pulsed discharge nozzle. The radical was produced by discharging a mixture of PH3 and C2H2 diluted in either Ar or Ne. A total of 25 hyperfine components of the 202–101 and 303–202 transitions have been measured which enabled us to precisely determine hyperfine coupling constants for both phosphorus and hydrogen nuclei. Spin densities on the phosphorus and β-carbon atoms, estimated from the hyperfine coupling constants, suggest that the radical forms an allenic structure (CP double bond) that is modified by a phosphoryl structure (CP triple bond), which is consistent with the theoretical estimation obtained previously by an ab initio calculation. The nature of the CP chemical bond in the radical is investigated in comparison with the corresponding nitrogen bearing counterparts.

Microwave spectrum of the CH3CCS radical in the 2E3/2 electronic ground state

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