The rotational spectrum, nuclear field shift effects, Pt nuclear spin-rotation constant, and electric dipole moment of PtSi

The pure rotational spectrum of the ground electronic state of platinum monosilicide has been measured for nine isotopomers. For the most abundant isotopomer, ¹⁹⁴Pt²⁸Si, the J=1-0 and the J=2-1 transitions were recorded up to the fourth vibrationally excited state. The data set obtained enabled a multi-isotopomer fit to a Dunham-type expression and the constants Y₀₁, Y₀₂, Y₁₁, Y₂₁, and Y₃₁ were determined. In the process of fitting the data it was necessary to include Born-Oppenheimer breakdown correction terms and the values and significance of these terms are discussed. Strong evidence is presented indicating within the rotational spectrum the presence of field shift effects due to the finite size of the Pt nucleus. The nuclear spin-rotation constant, C_I(¹⁹⁵Pt) is found to be 30.98(157) kHz in the ground vibrational state. Hyperfine structure arising from the ²⁹Si nucleus was not observed. The measurement of Stark shifts in the rotational spectrum of PtSi has enabled the determination of the dipole moments for the ¹⁹⁴Pt²⁸Si and ¹⁹⁶Pt²⁸Si isotopomers.     

The Sn, Sn and Sn nuclear spin-rotation constants in stannous monoxide, SnO, and a new multi-isotopomer analysis

A Fourier transform microwave spectrometer has been used to make high resolution measurements on the J = 1-0 rotational transition for 11 isotopomers of SnO. For the most abundant isotopomer the transition was observed in the v = 0, 1, 2, and 3 states. Magnetic hyperfine structure was observed in the transitions for ¹¹⁵Sn¹⁶O, ¹¹⁷Sn¹⁶O and ¹¹⁹Sn¹⁶O. The nuclear spin-rotation constant C_I(Sn) has been determined for these isotopomers for the first time and these constants have been related to nmr shielding parameters. A multi-isotopomer analysis, including data from the ¹²⁰Sn¹⁷O and ¹²⁰Sn¹⁸O isotopomers, has been performed on the data. Born-Oppenheimer breakdown parameters were required in the fit and these parameters have been compared to those for the other Sn-chalcogenides.     

Microwave spectroscopy, Dunham analysis, and hyperfine splittings of the isotopomers of zinc monosulfide, ZnS

Two rotational transitions of the first six vibrational states of three isotopomers of zinc monosulfide, ⁶⁴Zn³²S, ⁶⁶Zn³²S, and ⁶⁸Zn³²S, have been observed in cavity Fourier transform microwave (FTMW) spectroscopy. In addition, the hyperfine splitting of the ⁶⁷Zn³²S due to the nuclear quadrupole coupling constant of the I = 5/2 ⁶⁷Zn nucleus was observed for two rotational transitions of v = 0. The zinc sulfide was produced by laser ablation of a zinc rod with the resulting zinc plasma reacting with 0.6% OCS in argon in a pulsed jet originating upstream of the ablation plasma. A Dunham expansion of the rotational constant is performed resulting in the determination of B_e, α_e, γ_e, δ_e, and ε_e (Y₀₁, −Y₁₁, Y₂₁, Y₃₁, and Y₄₁) for ZnS. There is no evidence of Born–Oppenheimer breakdown in the mass-scaling of these parameters to within our experimental accuracy. χ_aa(⁶⁷Zn) of ⁶⁷Zn³²S is also determined.     

The ν3 bands of HOBr around 16 μm measured by high-resolution Fourier-transform spectroscopy

The ν₃ bands of HOBr around 16 μm have been recorded using high-resolution Fourier-transform absorption spectroscopy. More than 800 lines of the two main isotopomers, HO⁷⁹Br and HO⁸¹Br, with K_a values up to 4 and J values up to 41 have been assigned. Rotational and centrifugal distortion constants of the v₃=1 states were determined from a non-linear least-squares fit using an A-reduced Watson-type Hamiltonian. The results improve Hamiltonian constants determined previously from microwave spectroscopy, and accurate vibrational band centers are determined for the first time: 620.22855 (25) and 618.90606 (25) cm⁻¹ for the HO⁷⁹Br and HO⁸¹Br isotopomers, respectively.     

Microwave spectra of the Cl and Cl isotopomers of dichloromethylene: Nuclear quadrupole-, spin-rotation-, and nuclear shielding constants from the hyperfine structures of rotational lines

The rotational spectra of the isotopomers C³⁵Cl³⁷Cl and C³⁷Cl₂ of dichloromethylene in the ground vibronic state were recorded in the range 10-33 GHz using a molecular beam Fourier transform microwave spectrometer. CCl₂ was generated by flash pyrolysis using different precursors. The observed spectra were analyzed to yield rotational and centrifugal distortion constants, as well as the complete Cl nuclear quadrupole coupling tensors and the spin-rotation interaction constants from the hyperfine structure of the rotational lines. With inclusion of data from previous work on the most abundant species C³⁵Cl₂ [N. Hansen, H. Mäder, F. Temps, Phys. Chem. Chem. Phys. (3) (2001) 50-55.] a refined r₀ structure was determined. The spin-rotation interaction constants of all three isotopomers were used to derive ³⁵Cl and ³⁷Cl principal inertial axis nuclear magnetic shielding components which have not yet been determined by NMR spectroscopy.     

The pure rotational spectra of the lanthanum monohalides, LaF, LaCl, LaBr, LaI

Pure rotational spectra have been measured for all the major isotopomers of the lanthanum monohalides, LaF, LaCl, LaBr, and LaI, in their ground and (except for ) excited vibrational states. The spectra were observed with a cavity pulsed jet Fourier transform microwave spectrometer in the frequency range 5-24 GHz. The molecules were prepared by laser ablation of La metal and allowing the resulting plasma to react with SF₆, Cl₂, Br₂, or CH₃I precursor in an Ar carrier gas of the pulsed jet. For LaBr this is the first reported spectrum of any kind. Rotational constants, centrifugal distortion constants, nuclear quadrupole coupling constants, and nuclear spin-rotation constants have been determined for all the molecules. Accurate equilibrium (r_e) internuclear distances have given an indication of where the Born-Oppenheimer approximation is beginning to fail. From the centrifugal distortion constants and vibration-rotation (α_e) constants good estimates of the harmonic vibration frequencies and bond dissociation energies have been obtained. The halogen nuclear quadrupole coupling constants indicate the molecules to be highly ionic.     

Experimental determination of pressure-broadening parameters of millimeter-wave transitions of HNO3 perturbed by N2 and O2, and of their temperature dependences

We report on linewidth measurements on the J=24_K,11−23_K^′,10 and J=38_K,33−37_K^′,32 millimeter wave transitions in the ground vibrational state of nitric acid, located near 470.23 and 544.36 GHz, respectively. Experiments were performed with N₂ and O₂ as perturber molecules, in the 240-350 K temperature range by using a video-type spectrometer. The foreign-gas broadening parameters and their temperature dependence coefficients were determined using the Voigt profile, no narrowing effect being observed. In order to check the reliability of reported values, we carried out measurements on the J=14_K,12−13_K^′,11 transition located near 206.6 GHz, previously observed in two other laboratories. For this last line all the reported values are consistent themselves within one claimed standard deviation.     

The microwave spectrum of HGeCl

The J = 1₀₁-0₀₀ and 2₀₂-1₀₁ transitions of nine isotopomers of chlorogermylene, H⁷⁴Ge³⁵Cl, H⁷⁴Ge³⁷Cl, H⁷²Ge³⁵Cl, H⁷²Ge³⁷Cl, H⁷⁰Ge³⁵Cl, H⁷⁰Ge³⁷Cl, H⁷⁶Ge³⁵Cl, H⁷⁶Ge³⁷Cl, and H⁷³Ge³⁵Cl are measured at 8-9 and 16-18 GHz. The effective rotational constants, the nuclear quadrupole coupling constants of ³⁵Cl, ³⁷Cl, and ⁷³Ge, and the nuclear spin-rotation coupling constants of ³⁵Cl and ³⁷Cl are determined.     

Microwave rotational spectra of the Kr-NH3 van der Waals complex

Rotational spectra of the Kr-NH₃ van der Waals complex were measured in the frequency range between 4 and 24 GHz using a pulsed jet cavity Fourier transform microwave spectrometer. The isotopomers studied included those of NH₃, ¹⁵NH₃, ND₃, NHD₂, and NH₂D with the five most abundant isotopes of Kr. Tunnelling splittings due to the inversion of the ammonia subunit within the ground state of the complex were observed for all three deuterium containing isotopomers. In the NH₃ and ¹⁵NH₃ isotopomers, one of the tunnelling states has a spin statistical weight of zero and the splitting can therefore not be measured in these species. Nuclear quadrupole hyperfine structure arising from the ¹⁴N and ⁸³Kr nuclei was measured and the corresponding nuclear quadrupole coupling constants were determined. These were used to estimate structural parameters and derive information about the intermolecular dynamics. Smaller nuclear quadrupole splittings arising from the deuterium nuclei were observed but could not be resolved. The ground state spectroscopic constants were compared with experimental and theoretical data previously reported for Ar-NH₃ and its isotopomers. For the Kr-ND₃ isotopomers, additional transitions were observed and assigned to the two inversion components of an excited internal rotor state. A fit of the spectroscopic constants revealed the presence of a Coriolis perturbation, similar to that reported for this state in Ar-ND₃ and Ar-NH₃.     

The infrared spectra of 12C32S, 12C34S, 13C32S,and 12C33S

Using a tunable diode laser spectrometer, the infrared absorption spectra of four isotopic species of carbon monosulfide have been observed in the positive column of a dc discharge of CS₂ and Ar. The wavenumbers of 115 vibration-rotation transitions between 1180.5 and 1266.1 cm^?1 have been measured. These lines were assigned to the 1-0, 2-1, 3-2, and 4-3 bands of ¹²C³²S, the 1-0 and 2-1 bands of ¹²C³⁴S and ¹³C³²S, and the 1-0 band of ¹²C³³S. These new data have been combined with the previous infrared and microwave results to determine Dunham coefficients (Y_ij), the Dunham potential expansion constants (a₀,a₁,a₂,a₃, and a₄), and the classical turning points by the RKR method.     

The millimeterwave spectrum of germyl fluoride: Determination and comparison of the effective, substitution, and equilibrium structures

The ground state rotational spectrum of germyl fluoride was measured up to 1273 GHz (J ≤ 63). The rotational constants and quartic and sextic centrifugal distortion constants have been determined accurately for five isotopic species in natural abundance (^{70/72/73/74/76}Ge). The high accuracy of the rotational constants of these five isotopomers allowed us to study the mass dependence of the substitution coordinate of Ge. Equilibrium rotational constants of ⁷⁴GeH₃F were deduced with the help of the axial rotational constant and the rotation-vibration interaction constants determined by high resolution infrared spectroscopy. The r₀, r_,I, and r_e structures of GeH₃F were determined.     

The ν3 and 2ν3 bands of SO3, SO3, SO3, and SO3

This sixth of a series of publications on the high-resolution rotation-vibration spectra of sulfur trioxide reports the results of a systematic study of the ν₃ and 2ν₃ infrared bands of the four symmetric top isotopomers ³²S¹⁶O₃, ³²S¹⁸O₃, ³⁴S¹⁶O₃, and ³⁴S¹⁸O₃. An internal coupling between the l=0(A₁^′) and l=2(E^′) levels of the 2ν₃ states was observed. This small perturbation results in a level crossing between |k−l|=9 and 12, in consequence of which the band origins of the A₁^′,l=0 “ghost” states could be determined to a high degree of accuracy. Ground and upper state rotational constants as well as vibrational anharmonicity constants are reported. The constants for the center-of-mass substituted species ³²S¹⁶O₃ and ³⁴S¹⁶O₃ vary only slightly, as do the constants for the ³²S¹⁸O₃, ³⁴S¹⁸O₃ pair. The S-O bond lengths for the vibrational ground states of the species ³²S¹⁶O₃, ³⁴S¹⁶O₃, ³²S¹⁸O₃, and ³⁴S¹⁸O₃ are, respectively, 141.981 99(1), 141.979 38(6), 141.972 78(8), and 141.969 93(8) pm, where the uncertainties, given in parentheses, are two standard deviations and refer to the last digits of the associated quantity.     

Nuclear quadrupole coupling in chloroform and calibration of ab initio calculations

The complex hyperfine structures in the J = 1 ← 0, and J = 2 ← 1 ground state rotational transitions of ³⁵Cl₃CH and ³⁵Cl₂³⁷ClCH were resolved and measured at conditions of supersonic expansion. Accurate spectroscopic constants for the two isotopomers have been derived from global fits of the hyperfine structure together with hyperfine-free high-J millimetre wave data. The complete inertial and principal quadrupole tensors of the chlorine nuclei have been determined, and the symmetric top treatment for ³⁵Cl₃CH and the asymmetric top treatment for ³⁵Cl₂³⁷ClCH yield identical results for the principal tensor components of the ³⁵Cl nucleus. The availability of precise experimental splitting constants for many molecules allows benchmarking of ab initio field gradient calculations, and it is found that for the chlorine nucleus optimum predictive performance for molecules of moderate size is obtained at the B3LYP/aug-cc-pVDZ level by using a scaling factor of 1.0619(23).     

Rotational spectra and internal dynamics of Ne—H2S

Rotational spectra of 15 isotopomers of the Ne-H₂S van der Waals complex were measured in the frequency range 4–22 GHz using a pulsed molecular beam Fourier transform spectrometer. Two K = 0 progressions were observed for each of the symmetric isotopomers (with H₂S or D₂S). This doubling is attributed to an internal rotation motion of the H₂S subunit within the complex. These two states can be correlated with the 0₀₀ and 1₀₁ rotational states of free H₂S and D₂S. By contrast, symmetry constraints no longer apply to isotopomers with DHS. The excited internal rotor state is no longer metastable, and only one K = 0 progression could be observed. The rotational constants obtained were compared with those of Ar-H₂S and Ar—H₂O. The ground state rotational constant remained almost constant upon substitution of H with D, showing an unusual isotope effect, similarly to a previous observation in Ar-H₂S (GUTOWSKY, H. S., EMILSSON, T., and ARUNAN, E., 1997, J. chem. Phys., 106, 5309). This behaviour is in agreement with the ab initio study by OLIVEIRA, G. D., and DYKSTRA, C. E., 1999, J. chem. Phys., 110, 289. An approximate substitution analysis was carried out to deduce structural information from the ground state rotational constants. Nuclear quadrupole hyperfine structures were observed and resolved or partially resolved for isotopomers containing ³³S and D, respectively, and the corresponding nuclear quadrupole coupling constants were determined. These were used to derive information about the internal dynamics of the dimer. Different sensitivities of the quadrupole coupling constants of D and ³³S to the extent of out-of-plane motion were revealed.     

Search for low-energy induced depletion of Hf at the SPring-8 synchrotron

Electromagnetic transitions within nuclei reflect specific aspects of nuclear structure. This is particularly true for metastable excited states, or isomers, like ¹⁷⁸Hf^m2 (T_1/2=31${\mathrm{T}}_{1/2}=31$ years, excitation energy 2446 keV). The interaction of external radiation with isomers can be used to study atomic and nuclear properties and, perhaps, to induce a release of the stored energy. Some experiments indicated that low-energy photons near the L₃ edge (9.561 keV) of hafnium could cause this to occur for ¹⁷⁸Hf^m2, but the lack of a viable physical model and null experiments by other groups have left these claims in doubt. The present work describes a new experiment to examine this process by closely duplicating the irradiation conditions in positive studies, but using a more advanced multi-detector γ array. No support for an induced depletion of ¹⁷⁸Hf^m2 by low-energy photons was obtained, with an upper limit for the integral cross section that is eight orders-of-magnitude below the reported value.     

Ion-pair states of I<Subscript>2</Subscript>, Br<Subscript>2</Subscript>, IBr,and ICl

The experimentally determined energies and rotational constants of the vibrational levels v = 0–20 of the Ion-Pair states Ω = 0⁺, Ω = 1 of the I₂, Br₂, IBr, and ICl molecules are modeled. The model used includes three diabatic states, which correlate to X⁺(3P, 1D) + Y^～(1S₀). These states are coupled by the spin-orbit interaction, which is assumed to be independent of the internuclear distance. For IBr and ICl, as well as for the ungerade states of I₂ and Br₂, satisfactory results are obtained. The model is less applicable to the gerade states of I₂ and Br₂, which is possibly results from the retainment of the asymptotic J _A J _B coupling of the angular momenta at equilibrium internuclear distances.     

Absorption profiles of HCl for the J = 1-0 rotational transition: Foreign-gas effects measured for N2, O2, and Ar

Line profiles of the J = 1-0 transition of the hydrogen chloride, H³⁵Cl and H³⁷Cl isotopomers, were measured with a BWO-based submillimeter-wave spectrometer at AIST in real form: three hyperfine transitions for each isotopomer, i.e., total six lines at 625 and 626 GHz. The effect of foreign gases on the broadening and shift was determined for N₂, O₂, and Ar. The modified Voigt function was applied as the line shape function for preliminary analysis, where the collisional-narrowing effect was clearly observed. In the final analysis, we applied the Galatry function and determined the integral intensity, line center position, Lorentzian width, and contraction parameter for each absorption line. The magnitudes of the foreign-gas pressure-broadening coefficients decrease in order of N₂, O₂, and Ar. The line-shift coefficients were clearly observed, the magnitudes of which decrease in order of Ar, O₂, and N₂. The pressure dependence of contraction parameter was determined, although with poor precision.     

Analysis of ν2 of H2Se

The infrared absorption spectrum of ν₂ of H₂Se in the region from 885 to 1347 cm^?1 was obtained with a resolution limit of 0.025 cm^?1 on the University of Denver 50-cm FTIR spectrometer system. We have assigned 1604 lines for the six isotopomers of H₂Se, including 25 lines for the H₂⁷⁴Se isotopomer, and have analyzed them using Watson's A-reduced Hamiltonian in the I^r rotational representation. Ground state constants for each of the five most abundant isotopomers were obtained from fits of microwave transitions combined with weighted averaged ground state combination differences formed from the infrared bands (010), (020), (100), and (001). Upper state constants for each of the five most abundant isotopomers were obtained from least-squares fits of the spectral lines of ν₂, keeping the ground state constants fixed to the values determined from our ground state fits. An alternate set of ground state constants together with isotopic mass adjustment constants for all six isotopomers was determined by simultaneously fitting all available microwave transitions and infrared ground state combination differences. Keeping this set of ground state constants fixed, a single set of upper state constants and isotopic mass adjustment constants for the ν₂ band was determined by a simultaneous fit of infrared spectral lines from all six isotopomers.     

Rotational Spectroscopy of HBS: The Quadrupole Coupling Constant of S in Thioborine

The unstable HBS molecule has been produced in the gas phase by a high-temperature reaction between crystalline boron and hydrogen sulfide. Ground state rotational spectra have been observed in the millimeter-wave region, from 75 to 460 GHz, for the previously unobserved H¹¹B³³S and H¹⁰B³³S isotopic species. The analysis of the hyperfine structure produced by the ^10/11B and ³³S nuclear spins in the low-J rotational transitions has yielded the first evaluation of the quadrupole coupling constant of 33S in the thioborine molecule, which was 6.361(15) MHz in H¹¹B³³S and 6.329(17) MHz in H¹⁰B³³S. In addition, further measurements have been performed for the most abundant isotopomers H^10/11B^32/34S, for which improved values of rotational, centrifugal, and hyperfine structure constants have been determined.     

Control of luminescence and conductivity of delafossite-type CuYO2 by substitution of rare earth cation (Eu, Tb) and/or Ca cation for Y cation

Delafossite-type oxides of CuTb_yY_1−yO₂, CuEu_yY_1−yO₂, CuCa_xTb_yY_1−x−yO₂ and CuCa_xEu_yY_1−x−yO₂ have been prepared by solid state reactions. The lattice-parameter dependence on the composition implies substitution of the Tb³⁺, Eu³⁺ and Ca²⁺ cations for the Y³⁺ site. Noticeable sharp emission lines due to the f-f transitions (⁵D₄→⁷F_J, J=3-6) of Tb³⁺ or due to the f-f transitions (⁵D₀→⁷F_J, J=0-4) of Eu³⁺ are observed at room temperature. Electrical conductivities of CuCa_xTb_yY_1−x−yO₂ and CuCa_xEu_yY_1−x−yO₂ are larger than those of CuTb_yY_1−yO₂ and CuEu_yY_1−yO₂, indicating the increase of the hole concentration caused by the substitution of Ca²⁺ for the Y³⁺ site. These results indicate the controllability of the luminescence and conductivity in CuCa_xTb_yY_1−x−yO₂ and CuCa_xEu_yY_1−x−yO₂ delafossite-type oxides by simultaneous substitution of the rare earth Tb³⁺ or Eu³⁺ cation and the Ca²⁺ cation for the Y³⁺ site.