Search

The rotational spectra of CoNO were measured using a Fourier-transform microwave (FTMW) spectrometer. The CoNO molecules were generated in supersonic jets using the pulse-discharge reaction of Co(CO)3NO diluted with Ar. The amount of CoNO generated under the present experimental conditions was significantly more than that of CoCO, although the CO contained in a molecule of the precursor Co(CO)3NO is three times more than NO. The quadrupole parameter of the N nucleus was determined for a transition metal mononitrosyl complex for the first time and compared with those of other nitrosyl compounds.

The rotational spectra of AgCN and AuCN were measured using a Fourier-transform microwave (FTMW) spectrometer. AgCN and AuCN were generated in supersonic jets using the pulse-discharge reaction of laser-ablated metal atoms with HCN diluted with Ar. The rotational transitions for 107AgCN, 109AgCN, and AuCN were measured. The quadrupole parameters of the Au and N nuclei were compared with those of other metal monocyanides.

The rotational spectrum of the AgS radical in the X2Πi state was observed using a source-modulation microwave spectrometer. This radical was generated in a free-space cell by a DC glow discharge under Ar-diluted H2S. Silver atoms were supplied by sputtering from silver sheets placed on the inner surface of the stainless steel cathode. Rotational transitions from J = 7.5 – 6.5 to 39.5 – 38.5 were measured in the 58–310 GHz region. Rotational, centrifugal distortion, and several fine- and hyperfine-structure constants were determined by least-squares analysis. Other spectroscopic parameters such as the dissociation energy, vibrational wavenumber, and equilibrium bond length were also derived from the determined molecular constants. In addition, some electronic properties were estimated from the fine- and hyperfine-structure constants.

The millimeter- and submillimeter-wave spectra of PtS in the X 3 Σ 0 - state were observed by employing a source-modulated microwave spectrometer. The PtS radical was generated in a free space cell by using a dc glow plasma of H2S and Ar. Platinum atoms were supplied from a small piece of platinum sheet lining the inner surface of a stainless steel cathode by the sputtering reaction. Rotational transitions were recorded for four dominant isotopomers, 194PtS, 195PtS, 196PtS, and 198PtS in the X 3 Σ 0 - ground state, and the spectroscopic constants for each isotopomer were determined using a Hund’s case (c) Hamiltonian. The lower limit of the 3 Σ 0 − - 3 Σ 1 − energy separation is estimated from a Hund’s case (a) analysis.

The rotational spectra of NiCO and PdCO in the ground and ν(2) excited vibrational states were observed by employing a source-modulated microwave spectrometer. The NiCO and PdCO molecules were generated in a free space cell by the sputtering reaction of nickel and palladium sheets, respectively, lining the inner surface of a stainless steel cathode with a dc glow plasma of CO and Ar. The molecular constants of NiCO and PdCO were determined by least-squares analysis. By force field analysis for the molecular constants of not only NiCO and PdCO but also of PtCO as previously reported, the harmonic force constants were determined for these three group 10 metal monocarbonyls. The vibrational wavenumbers derived for the lower M-C stretching vibrations were in good agreement with those obtained from the IR spectra in noble gas matrices and those predicted by several quantum chemical calculations published in the past. The bending vibrational wavenumbers derived by the force field analysis were also consistent with most quantum chemical calculations previously reported, but showed systematic discrepancies from the matrix IR values by about 40 cm(-1), even after reassignment (ν(2) band → 2ν(2) band) of the matrix IR spectra of PdCO and PtCO.

Monomeric platinum cyanide, PtCN, was detected in the gas phase by employing a source-modulated microwave spectrometer. The PtCN radical was generated in a free space cell using the sputtering reaction from a platinum sheet placed on the inner surface of a stainless steel cathode through a dc glow plasma of CH 3 CN diluted with Ar. The rotational constants obtained for several isotopomers indicated that the monomeric platinum cyanide is in a cyanide form (PtCN) and not in an isocyanide form (PtNC). Observed fine- and hyperfine-spectral patterns suggest that the PtCN radical has the 2 Δ 5 / 2 electronic ground state.

The chemistry of the group 11 metal cyanide system has been of considerable interest because of the commercial importance of some of the complexes formed in this system. These metal cyanides contain one-dimensional linear -M-CN-M-CN-M- chains in the solid state; however, they have not been observed as free monomeric species. This Article reports the first detection of monomeric AgCN and AuCN in the gas phase by using rotational spectroscopy. The sputtering reaction of silver and/or gold sheets placed on a stainless steel cathode with CH3CN diluted in Ar resulted in the production of AgCN and AuCN spectra. Spectroscopic observation of the parent and several rare isotopic species allowed the determination of r(0), r(s), r(Iepsilon), r(m)(1), and r(m)(2) structures in the case of AgCN and r(0) and r(s) structures in the case of AuCN. All data indicate that these two species have a linear MCN geometry with a low-energy bending vibration.

The rotational spectrum of the NiS radical in the X(3)Sigma(-) state was observed by employing a source-modulation microwave spectrometer. The NiS radical was generated in a free space cell by a dc glow discharge in H(2)S diluted with Ar. The nickel atoms were supplied by the sputtering reaction from a nickel cathode. Rotational transitions with J = 11-10 to 25-24 were measured in the region between 135 and 314 GHz. Rotational, centrifugal distortion and several fine-structure constants were determined by a least-squares analysis. Other spectroscopic parameters such as dissociation energy, vibrational wavenumber and equilibrium bond length were also derived from the determined molecular constants. Excitation energies of the lowest (3)Pi and (1)Sigma(+) states were estimated from the fine-structure constants, lambda and gamma.

The rotational transitions of AuH and AuD with the hyperfine structure due to the gold nucleus (I = 3/2) were observed in the 220, 430, and 650 GHz regions with source modulation microwave spectrometers. The AuH and AuD molecules were generated by sputtering from a gold sheet lining the inner surface of a stainless-steel cathode in a dc glow discharge through hydrogen and deuterium gases, respectively, diluted with argon gas. The nuclear electric quadrupole coupling constant and the nuclear magnetic spin-rotation coupling constant were determined for each isotopomer by a least-squares analysis.

The pure rotational spectrum of AuO in the X 2 Π 3/2 state was observed by employing a source-modulated microwave spectrometer. The AuO radical was generated in a free space cell by the sputtering reaction from a gold sheet lining the inner surface of a stainless steel cathode using a dc glow plasma of O 2 and Ar. Observation of the rotational transitions in both the ground and first excited vibrational states enabled to determine molecular constants by a least-squares fit. Other spectroscopic parameters such as equilibrium bond length, r e , and vibrational wavenumber, ω e , were also derived from the obtained molecular constants.

The millimeter- and submillimeter-wave spectra of PtCO in the ground and ν 2 excited vibrational states were observed by employing a source-modulated microwave spectrometer. The PtCO molecule was generated in a free space cell by the sputtering reaction from a platinum sheet lining the inner surface of a stainless steel cathode using a dc glow plasma of CO and Ar. From the molecular constants determined for the ν 2 excited state, especially the l -type doubling constant, its harmonic wavenumber was determined to be ≈420 cm −1 , which resolved the reported discrepancy between the previous matrix-infrared and theoretical estimates.

The rotational spectra of the CrF and CrCl radicals in the X 6Sigma+ state were observed by employing a Fourier transform microwave spectrometer. The CrF and CrCl radicals were generated by the reaction of laser-ablated Cr with F2 and Cl2, respectively, diluted in Ar. A chromium rod made of chromium powder pasted with epoxy resin was ablated by a Nd:YAG laser. Rotational transitions were measured in the region between 8 and 26 GHz. Several hyperfine constants due to the halogen nuclei were determined by a least-squares analysis. The electronic properties of CrF and CrCl were derived from their hyperfine constants and were compared with those of other 3d transition metal monohalides: TiF, MnF, FeF, CoF, NiF, and FeCl.

The rotational spectrum of the CoF radical in the X 3 Φ 4 state was observed by employing a source modulation microwave spectrometer. The CoF radical was generated in a free space cell by a dc glow discharge in CF4 and He. The cobalt atoms were supplied by the sputtering reaction from cobalt powder placed over a lower surface of the cylindrical electrodes. The transitions with J=11–10 to 17–16 were measured in the region between 250 and 400 GHz. The effective rotational, centrifugal distortion, and hyperfine constants were obtained by a least-squares analysis.

The millimeter- and submillimeter-wave spectra of AuCl and AuBr in the X1Σ+ states were observed by employing a source-modulated microwave spectrometer. The AuCl and AuBr molecules were, respectively, generated in a free space cell by a d.c. glow discharge in Cl2 and Br2 with Ar. The gold atoms were supplied by the sputtering reaction from a gold sheet placed on the inner surface of a stainless-steel cathode. Rotational transitions of Au 35 Cl , Au 37 Cl , Au 79 Br , and Au 81 Br in highly excited vibrational states as well as in the ground vibrational states were measured in the region between 189 and 314 GHz. The transition frequencies were analyzed by a least-squares method using a combined-isotopomer Dunham-type term energy expression. The potential constants of gold halides obtained were compared with those of copper and silver halides.

The millimeter- and submillimeter-wave spectrum of AuF in the X 1 Σ + state was observed by employing a source-modulated microwave spectrometer. The AuF molecule was generated in a free space cell by the sputtering reaction from a gold sheet lining the inner surface of a stainless steel cathode using a dc glow plasma of CF 4 and Ar. Rotational transitions in the highly excited vibrational states enabled to determine Dunham-type molecular constants by a least-squares fit. Other constants like dissociation energy D e , vibrational wavenumber ω e and its anharmonic term ω e x e were also derived from the obtained constants.

The millimeter- and submillimeter-wave spectra of CuF and AgF in the X1Σ+ states were observed by employing a source-modulated microwave spectrometer. The CuF and AgF molecules were generated in a free space cell by a dc glow discharge in CF4 and Ar. The copper and silver atoms were respectively supplied by sputtering from a copper cathode and silver sheets placed on the inner surface of a stainless-steel cathode. Rotational transitions of 63CuF, 65CuF, 107AgF, and 109AgF in highly excited and ground vibrational states were measured in the region between 200 and 400 GHz. The transition frequencies were analyzed by a least-squares method using a combined-isotopomer Dunham-type term energy expression.

The rotational spectra of NiF in the electronic ground (2)Pi state and the lowest electronically excited (2)Sigma state have been observed. The source of nickel atom was sputtering from a nickel electrode or nickel powder placed on a stainless steel electrode. The molecular constants have been determined by a least-squares analysis of the observed transition frequencies. The rapid increase in the Lambda-type splittings in the ground state reveals that the observed rotational transitions are ascribed to the spin substate (2)Pi(3/2). The rotational transitions corresponding to the other substate,(2)Pi(1/2), have not been observed. The large spin-rotation interaction constant gamma in the electronically excited (2)Sigma state is consistent with that from the electronic spectroscopy. Copyright 2001 Academic Press.

The trifluorosilyl radical has been produced by glow discharge in hexafluorodisilane in a free space cell. The rotational spectrum of the radical has been measured from the 330 (N=22−21) GHz region down to the 90 (N=6−5) and 75 (N=5−4) GHz regions. In the lower N transitions the K=1 hyperfine components showed a distinct splitting. From the splitting of the K=1 lines it was concluded that the spin-rotation interaction constant of trifluorosilyl radical has a positive sign, which is different from that of trifluoromethyl. This difference is discussed in terms of the electronic states. The simplified discussion based on the Mulliken–Walsh diagram of the energy level is used to rationalize the difference in the sign of the interaction constants in the two radicals. The Si–F bond length is determined from the rotational constant B0 to be 1.565 A when the bond angle F–Si–F is assumed to be 109.9° deduced in the matrix infrared spectroscopy. The spin density on the fluorine atoms is derived from the hyperfine c...

The rotational spectrum of the NI radical in the X 3Σ− ground electronic state has been observed by a source modulated spectrometer with a free space cell. The NI radical was generated in the cell by a dc (direct current) glow discharge in a mixture of iodine vapor with N2 and He. A rotational transition consisted of a group of congested lines resulting from the hyperfine interactions due to both iodine and nitrogen nuclei. The molecular constants including the spin–spin and spin–rotation coupling constants and the magnetic and nuclear quadrupole hyperfine interaction constants were determined by the least-squares analysis. The spin density of the unpaired electrons was estimated from the observed hyperfine coupling constants to be 76.8% and 23.4% on the nitrogen and the iodine atoms, respectively. The quadrupole coupling constant was related with the difference in electronegativity of the two bonded atoms.

The microwave spectra of P14N16O and its isotopomers P15N16O and P14N18O were observed in a dc glow discharge plasma of a mixture of nitric oxide and hydrogen gases over solid red phosphorus placed on the stainless steel electrode. Rotational transitions of the parent P14N16O species were measured in the ground state as well as in the vibrationally excited ν1 (PN str.), ν2 (bend), and 2ν2 states. The l=0 substate of the 2ν2 state interacts with the ν1 state through a Fermi resonance. The rotational constants determined for the ground states of the three isotopomers yield the substitution structure, rs(PN)=151.6516(87) pm and rs(NO)=119.5025(80) pm.

The mechanism of propene–deuterium reaction over alumina-supported Rh and Ru carbonyl cluster complexes was studied with kinetic investigation as well as microwave spectroscopic analysis of monodeuteropropene. Irrespective of the nuclearity and the kind of metals, similar catalytic behavior was observed in both C 3 H 6 –C 3 D 6 and C 3 H 6 –D 2 reactions over Rh 4 (CO) 12 /Al 2 O 3 , Rh 6 (CO) 16 /Al 2 O 3 and Ru 3 (CO) 12 /Al 2 O 3 , suggesting the formation of common surface complexes as [M(CO) 2 ] n by impregnation. Different catalytic behavior of fixed carbonyl cluster complexes from that over freshly reduced metal surface (Rh/Al 2 O 3 ) and CO preadsorbed metal surface(CO/Rh/Al 2 O 3 ), suggests the existence of an unique catalytically active species such as metal–metal bridged hydrides for the hydrogen exchange process of propene molecules.

The millimeter-wave spectrum of HCCCCF was observed in the ground state as well as in the low-lying vibrationally excited states ν 7 , ν 8 , ν 9 and also associated ν 8 + ν 9 , 2ν 9 , and 3ν 9 states. The HCCCCF molecule was produced by a dc glow discharge in a flowing vapor of 2,3,4,5,6-pentafluorostyrene. The l -type doubling constants determined are in good agreement with the values predicted from the harmonic force field calculation.

The microwave spectrum of the NBr radical in the X 3Σ− ground electronic state has been observed by a source modulated spectrometer. The NBr radical was generated in a free space cell by a dc glow discharge in a mixture of N2, Br2, and He. The spectrum with three spin components of both two isotopomers, N79Br and N81Br, was observed. The spectrum showed complicated splitting by the hyperfine interactions due to both bromine and nitrogen nuclei. The molecular constants including the magnetic hyperfine and nuclear quadrupolar hyperfine interaction constants were determined by analyzing the observed spectrum. The spin density of the unpaired electrons was estimated from the observed hyperfine coupling constants to be 73.4% and 22.4% on the nitrogen and the bromine atoms, respectively.

The microwave spectra of the four isotopomers of the BrBO molecule (79Br10BO, 81Br10BO, 79Br11BO, and 81Br11BO) were observed in a dc glow discharge plasma of a mixture of boron tribromide vapor and oxygen gas. Rotational transitions of BrBO were measured for the ground state as well as for the vibrationally excited states, nu2 (bend) and nu3 (Br-B str.), for all of four isotopomers, and associated 2nu2, nu2 + nu3, and 2nu3 for the 11B species. The l = 0 substate of the 2nu2 state interacts with the nu3 state through the Fermi resonance. The rotational constants determined for the ground states of the four isotopomers yield the substitution structure, rs(Brsbond;B) = 1.835791(70) Å and rs(Bdbond;O) = 1.20472(25) Å. The pi character and ionic character of the Br-B bond, which are estimated from the bromine quadrupole coupling constant eQq, are discussed through the comparison with those of related molecules such as BrCN and BrBS. Copyright 1998 Academic Press.

The rotational spectrum of chromium monochloride in the 6Σ+ ground electronic state has been observed with a source-modulated microwave spectrometer in the millimeter-wave region. The CrCl radical was produced in a free space absorption cell by a dc glow discharge in a mixture of AlCl3 vapor and He using stainless steel electrodes. Chromium atom was supplied from the electrodes by the sputtering reaction. Observed spectral lines were analyzed by a least-squares fit and the molecular constants including the rotational and centrifugal distortion constants and the spin-spin and spin-rotation interaction constants were determined. The experimental rotational constants B0 for 52Cr35Cl and 52Cr37Cl are 5 009.345 69(69) and 4 847.851 00(32) MHz, respectively, where the uncertainties attached to the last digit correspond to one standard deviation.

The pure rotational spectra of 107AgO and 109AgO were recorded in the 117–380 GHz spectral region using a dc-sputtering absorption cell. The 107Ag(I=1/2) and 109Ag(I=1/2) magnetic hyperfine parameters are interpreted in terms of plausible electronic configuration contributions to the X 2Πi state. It is shown that the determined unusual sign of the Λ-doubling and Fermi contact parameters implies that the X 2Πi state is dominated by a three open shell configuration. A comparison with isovalent CuO is made.

The reactive species BBr was produced by the glow discharge of the BBr 3 vapor in a free space cell. Rotational spectra of the four isotopic species were observed between 117 and 480 GHz. For lower rotational transitions the hyperfine structure owing to the bromine nucleus has been observed, and from its analysis the nuclear quadrupole interaction constant has been determined. The breakdown of the Born-Oppenheimer approximation for the rotational constant was recognized and the relevant parameters were determined.

The rotational spectrum of the CrF radical in the X 6Σ+ state was observed by employing a source modulation microwave spectrometer. The CrF radical was generated in a free space cell by a dc glow discharge in CF4 and He. The chromium atom was supplied by the sputtering reaction from chromium powder placed over a lower surface of the cylindrical electrodes. The transitions with N=12−11 to 20−19 were measured in the region between 270 and 460 GHz. The rotational, centrifugal distortion and several fine‐structure constants were obtained by a least squares analysis.

The rotational spectrum of the FeCl radical in the electronic ground state was observed by using a source-modulated millimeter-wave spectrometer. This species was produced in a free-space cell by glow-discharging a mixture of helium and aluminum trichloride vapor. Iron atoms were extracted during the discharge from the stainless-steel electrodes in the cell. The spectrum was observed for the two lowest-lying spin components of the inverted sextet Δ state. The rotational and centrifugal distortion constants were determined by a least-squares fit to the line frequencies of each spin substate.

The effect on the rate and mechanisms of propene-deuterium reactions of dispersing ZrO2 on various supports such as silica, alumina, and titanium dioxide has been studied by microwave spectroscopic analysis of monodeuteropropene as well as by kinetic investigation. By dispersal of ZrO2 on these supports, the rate of the C3H6-D2 reactions is increased considerbly compared to that over unsupported ZrO2, with the decrease of activation energy. Hydrogen exchange in propene proceeds simultaneously with addition via the associative mechanism through n-propyl and s-propyl intermediates. Through XPS analysis of ZrO2/SiO2, it was found that a monolayer of ZrO2 is formed over the silica support. The monolayer catalyst exhibits catalytic behavior quite different from that of unsupported ZrO2. On the other hand, alumina surfaces modified by ZrO2 layers may be the main active sites in the case of ZrO2/Al2O3. The marked enhancement of the reaction rate in the lower loading region of ZrO2/TiO2 may be explained by the strong interaction of atomically dispersed zirconium ions with active centers on TiO2.

The microwave spectrum of the SiBr+ cation has been observed. The reactive species was generated in a free-space cell by a discharge through pure SiBr4 gas. In addition to the spectra of both 28Si79Br+ and 28Si81Br+ species, those of the less abundant isotopic species of silicon, 29Si and 30Si, are also observed. The spectrum was analyzed using a Dunham expansion for the rotational energy levels. The SiBr equilibrium bond length is determined to be 2.095456(5) A. From the nuclear quadrupole coupling constant the ionic character of the SiBr bond is calculated to be 86%.

The contributions of Professor Morino's research work to the understanding of molecular structure are reviewed chronologically: early studies in Tokyo (1930–1943), studies at Nagoya University (1943–1948), at the University of Tokyo (1948–1969), and at Sagami Chemical Research Center (1969–present).

The mechanism of propene–deuterium reaction over unsupported and silica-supported ZrO2 catalysts was studied with kinetic investigation as well as microwave spectroscopic analysis of monodeuteriopropene. Unsupported ZrO2 exhibited the identical catalytic behavior for C3H6–D2 reaction with other oxide catalysts previously reported: Only propane-d2 was selectively formed in the addition process, with no hydrogen exchange in propene. By supporting on silica, the rate of C3H6–D2 reaction increased considerably, with the decrease of activation energy. Hydrogen exchange in propene proceeded simultaneously with addition via associative mechanism through propyl and isopropyl intermediates. Small particles of ZrO2 were proposed as active sites of this characteristic catalytic behavior.

The microwave spectra of fluorocyanobutadiyne, FC5N, in the ground, v11 (skeletal bending) and 2v11 states were observed with a source-modulated spectrometer. The FC5N molecule was generated in a free space absorption cell by a dc glow discharge in pentafluorobenzonitrile, C6F5CN. The rotational and centrifugal distortion constants for the ground state were determined to be 755.398325(41) MHz and 8.3458(11) Hz, respectively. The l-type doubling constant for the v11 state, 0.508887(48) MHz, was consistent with the value calculated from the harmonic force field.

The microwave spectrum of 1-fluoropropyne (CH 3 CCF) has been detected for the first time in the discharge plasma of 2,3,4,5,6-pentafluorotoluene (CH 3 C 6 F 5 ). Rotational transitions of CH 3 CCF with J = 30-29 to 38-37 were measured in the region between 207 and 262 GHz. The accurate molecular constants were determined to be B = 3451.46584(30) MHz, D J = 0.34071(13) kHz, and D JK = 43.090(11) kHz, where the uncertainties correspond to one standard deviation.

The famous Darling-Dennison resonance is fully discussed for the 32S 16O2 molecule by use of the classical treatment as well as by the Van Vleck contact transformation method. The conclusion is that the single-term approximation as a resonance phenomenon, originally proposed for the H2O molecule by Darling and Dennison, cannot be applied to the SO2 molecule, because the two frequencies, ν1 and ν3 are separated by too far a distance in the latter molecule. The force field of the SO2 molecule was calculated up to the quartic terms in order to confirm the above conclusions.

The microwave spectrum of 3,6-dihydro-1,2-dioxin, a cyclic peroxide derived from buta-1,3-diene, was measured in the frequency range 10–26 GHz. Rotational and centrifugal distortion constants were determined from a least-squares fit to the observed b -type rotational transition frequencies. The molecular structure is inferred on the basis of the rotational constants. The molecule is found to have a skewed boat form as found in cyclohexene. The NMR spectrum of the molecule was observed at temperatures down to −100°C and analyzed in terms of interchanging conformations. The activation energy and entropy of the puckering motion were derived.

The microwave spectra of fluoroiodoacetylene (ICCF) in the ground and the vibrationally excited states were observed with a source-modulated spectrometer. The ICCF molecule was generated in a free space absorption cell by a dc glow discharge in pentafluoroiodobenzene (C 6 F 5 I). Rotational transitions of ICCF in the range of J = 27-26 to 93-92 were measured not only in the ground state but also in the first vibrationally excited states ν 3 (I C stretch), ν 4 (CCF bend), and ν 5 (ICC bend). The rotational and centrifugal distortion constants obtained for the ground state are 1200.590266(77) MHz and 50.5314(54) Hz, respectively, where the uncertainties correspond to one standard deviation. The l -type doubling constants obtained are 0.312099(43) MHz for the ν 4 state and 0.66415(12) MHz for the ν 5 state, which are consistent with the values calculated from the harmonic force field. The iodine quadrupole coupling constant in the ground state (−2417(13) MHz) is in good agreement with that in the ν 3 state (−2416.1(99) MHz) within one standard error. Moreover, we discuss the π character and the ionic character of the I C bond from the iodine coupling constant.

Infrared spectroscopy and isotopic tracer technique with microwave spectroscopy revealed a marked change of reaction intermediates as well as reaction mechanisms by the presence of excess oxygen in NO-propene reaction over highly dispersed Rh/Al2O3 catalyst.

The rotational transitions of hydrogen isocyanide (HNC) and deuterium isocyanide (DNC) in the vibrationally excited states as well as in the ground states were observed in the millimeter and submillimeter wave region. These compounds were generated in a dc glow discharge plasma containing hydrogen (or deuterium), nitrogen, and carbon atoms. The stretching vibrational modes, ν1 and ν3 states, were selectively excited in the discharge plasma; on the other hand, the bending mode ν2 state was thermally populated at the cell temperature. The precise rotational, centrifugal distortion and l‐type doubling constants were obtained for all of the first vibrationally excited states as well as the ground states. The experimental equilibrium rotational constants Be are 45 496.7769(45) and 38 207.7217(105) MHz for HNC and DNC, respectively, where uncertainties correspond to one standard deviation. The equilibrium internuclear distances are also determined to be re (H–N)=0.996 0643(29) A and re (N≡C)=1.168 3506(16) A.

The structure of the AlOH molecule is investigated by the ab initio SCF and MP3 methods. The 6-311G and well-tempered Gaussian-type basis sets are supplemented by triple polarization functions. The most stable geometry is a bent form, with an AlOH angle of 163°. The potential energy curve for H rearrangement from HAlO to AlOH is calculated along with the vibrational frequencies and intensities. The stabilization energy due to bending of the AlOH angle is small in comparison with the zero-point vibrational energy of the bending mode. The experimental average structure of AlOH is expected to be linear.

The pure rotational spectrum of nickel monochloride in the 2Π3/2 ground electronic state has been observed in the laboratory for the first time in the millimeter- and submillimeter-wave region. The NiCl radical was generated in a free-space absorption cell by a DC glow discharge in a mixture of Cl2 and Ar using a nickel cathode, from which nickel atoms were supplied by the sputtering reaction. The rotational, centrifugal distortion, and fine-structure constants were determined by a least-squares method using an effective Hamiltonian for a 2Π3/2 electronic state.

The mechanism of the hydroformylation of propene over silica-supported Rh and Pd catalysts was studied by isotope tracer technique with microwave spectroscopy and infrared spectroscopic technique as well as kinetic investigation. The rate-determining steps in the hydroformylation process were different over the two metals: hydrogenation of surface acyl species on Rh catalysts and CO insertion into surface propyl species on Pd catalysts. The structure and the reactivity of the surface propyl intermediates were determined by analyzing the isotope distribution of monodeuteropropene formed during C 3 H 6 D 2 CO reaction with microwave spectroscopy. It was revealed that n -propyl species is more reactive for CO insertion than s -propyl species. Promotion effect of sodium cations on hydroformylation was also investigated in detail and different roles of sodium cations were demonstrated for Rh and Pd catalysts.

The microwave spectra of chlorofluoroacetylene (ClCCF) and bromofluoroacetylene (BrCCF) in the vibrationally excited states were observed with a source-modulated spectrometer. These compounds were generated in a free space absorption cell by a dc glow discharge in chloropentafluorobenzene (C 6 F 5 Cl) or bromopentafluorobenzene (C 6 F 5 Br). The rotational, centrifugal distortion and l -type doubling constants were obtained for the ν 5 states in ClCCF, and for the ν 4 and ν 5 states in BrCCF. The bromine quadrupole coupling constants of BrCCF in the excited states are well consistent with those in the ground state determined by Andolfatto et al. ( Z. Naturforsch. A 37 , 1449–1453 (1982)) with the Fourier transform microwave spectroscopy.

The microwave spectra of fluoroiodoacetylene (ICCF) in the ground and the vibrationally excited states were observed with a source-modulated spectrometer. The ICCF molecule was generated in a free space absorption cell by a dc glow discharge in pentafluoroiodobenzene (C 6 F 5 I). Rotational transitions of ICCF in the range of J = 27-26 to 93-92 were measured not only in the ground state but also in the first vibrationally excited states ν 3 (I C stretch), ν 4 (CCF bend), and ν 5 (ICC bend). The rotational and centrifugal distortion constants obtained for the ground state are 1200.590266(77) MHz and 50.5314(54) Hz, respectively, where the uncertainties correspond to one standard deviation. The l -type doubling constants obtained are 0.312099(43) MHz for the ν 4 state and 0.66415(12) MHz for the ν 5 state, which are consistent with the values calculated from the harmonic force field. The iodine quadrupole coupling constant in the ground state (−2417(13) MHz) is in good agreement with that in the ν 3 state (−2416.1(99) MHz) within one standard error. Moreover, we discuss the π character and the ionic character of the I C bond from the iodine coupling constant.

Fourier-transform microwave and millimeter-wave spectra of the iodomethyl radical, CH(2)I, have been observed in the ground vibronic state in the frequency ranges 17-38 GHz and 200-610 GHz, respectively. The pi-electron radical was produced either by iodine abstraction from diiodomethane (CH(2)I(2)) or by hydrogen abstraction from iodomethane (CH(3)I). Seventy-three hyperfine resolved lines owing to the two hydrogen and to the iodine nuclei have been detected in the microwave region, including K(a) = 0 (ortho species) and K(a) = 1 (para species). No hyperfine splitting due to the hydrogen nuclei could be observed for the para species, directly confirming the planarity of the radical and that the ground electronic state is (2)B(1). More than 400 a-type transitions that span the values N' < or = 35, K(a) < or = 6, were detected. A global least-squares analysis of the measured lines was conducted and led to the determination of an exhaustive list of molecular constants. In particular, the sign of the Fermi-contact constant of iodine was unambiguously determined to be negative, which is opposite to that of the other monosubstituted halomethyl radicals. This work allowed a systematic comparison of the structural and bonding properties among the CH(2)X analogues (where X = F, Cl, Br, and I) owing to the hyperfine coupling constants of both the hydrogen and halogen nuclei.