Submillimeter spectrum and spectroscopic constants of the arsine molecule in the ground vibrational state

The submillimeter spectrum of the arsine molecule, AsH₃, of both the allowed R-branch transitions (J + 1 ← J, J = 0, 1, 2, 3) and forbidden transitions of the Q branches, |K| = 4 ← 7, 5 ← 8, 6 ← 9, is investigated in the frequency range from 220 to 900 GHz. Weak absorption lines were observed by using the spectrometer RAD with sensitivity increased by a nontunable cavity cell. On the basis of the results obtained and microwave data available in the literature the rotational spectrum of the arsine molecule in the ground state is analyzed.     

Rotational spectrum and spectroscopic constants of the phosphine molecule in the ground vibrational state

A comprehensive investigation of both the allowed and the forbidden rotational spectra of the phosphine molecule, PH₃, in the ground vibrational state is described. The new experimental microwave investigation covers the frequency region from 300 to 1070 GHz.     

The ground state rotational constants of NNO

We report new measurements of the 5 ← 4 through 9 ← 8 lines in the pure rotational spectrum of nitrous oxide, ¹⁵N¹⁵N¹⁶O, and measurements at room temperature and at an elevated temperature of the 10⁰0-00⁰0 and 02⁰-00⁰0 bands of that molecule. The new data together with data for 10 other vibration-rotational transitions which previously have been reported enable us to determine the ground state constants. Using the newly determined values of B₀₀₀, D₀₀₀, and H₀₀₀, we have determined the band origins and the upper state constant differences B - B₀₀₀, D - D₀₀₀, and H - H₀₀₀ of 25 vibration-rotational bands whose lower level is the ground vibrational state.     

Far infrared spectrum and spectroscopic constants of AsH3 in the ground state

The far ir spectrum of arsine, AsH₃, was recorded in the range 25–100 cm^?1 with a resolution of approximately 0.004 cm^?1. ΔJ = +1, ΔK = 0 rotational transitions were measured and assigned up to J″ = 12. These transitions, together with the presently available microwave and submillimeter-wave data and ground state combination differences, were analyzed on the basis of a rotational Hamiltonian which includes Δk = ±3 and Δk = ±6 interaction terms. The derived ground state molecular parameters reproduced the transition frequencies of both allowed and “perturbation allowed” transitions within the accuracy of the measurements. The equilibrium structure was determined for the AsH₃ molecule.     

The submillimeter-wave spectrum and spectroscopic constants of SO2 in the ground state

The submillimeter-wave spectrum of SO₂ has been recorded with 0.004 cm^?1 resolution in the region 8–90 cm^?1. About 2000 lines were observed, 1500 of which have been assigned to the ground state rotational transitions of ³²SO₂. Molecular constants up to the 10th order have been derived, combining our data with the available microwave data in the literature. SO₂ rotational spectrum line positions up to 90 cm^?1 can be reproduced from these constants, within the experimental accuracy (2 × 10^?4 cm^?1).     

Far-infrared spectrum of sodium hydride

Rotational spectra in the v = 0, 1, 2, and 3 levels of the ground (¹Σ) state of sodium hydride have been observed using tunable far-infrared radiation generated from the difference frequency between two CO₂ lasers. The Dunham coefficients, which have been determined without the use of optical data or isotopic scaling relations, are Y₀₁ = 146 999.138(38) MHz, Y₀₂ = −10.29481(54) MHz, Y₀₃ = 6.243(49) × 10⁻⁴ MHz, Y₁₁ = −4109.912(68) MHz, Y₁₂ = 0.14695(68) MHz, Y₂₁ = 33.341(34) MHz, Y₂₂ = −2.69(20) × 10⁻³ MHz, and Y₃₁ = −1.0517(55) MHz. The constants are typically an order of magnitude more accurate than the best values previously available, and where comparison is possible, agreement is found to be excellent.     

The rotational spectrum of the ground state of methylamine

Recent progress is reported in measuring, assigning, and fitting the rotational spectrum of the ground vibrational state of methylamine, CH₃NH₂, a spectrum complicated both by internal rotation of the methyl top and by inversion of the amino group. New measurements of 513 rotational transitions with J up to 30 and K up to 9 were carried out between 49 and 326 GHz using the millimeter-wave spectrometer in Kharkov. After removing the observed quadrupole hyperfine splittings, these new data along with previously published measurements were fitted to a group-theoretical high-barrier tunneling Hamiltonian from the literature, using 53 parameters to give an overall weighted standard deviation of 0.80 for 850 far-infrared and 673 microwave transitions in the ground state. The root-mean-square deviation of 0.018 MHz obtained for 346 millimeter-wave transitions measured with 0.020 MHz uncertainty represents an approximately 30-fold improvement in fitting accuracy over past attempts.     

FT-FIR-spectrum and the ground state constants of D2CO

The ground state spectrum of the formaldehyde D₂¹³CO molecule in the range from 25 to 360 cm⁻¹ has been recorded by a Fourier transform infrared spectrometer. The quantum number limits of the assigned transitions are J = 6-54 and K_a = 0-16. The data was fitted into Watson’s A- and S-reduced Hamiltonians in I^r-representation up to eighth order. The determinable constants calculated from both reductions are compared. The standard deviation of the far infrared data is 3.0 MHz. The spectroscopic constants are also calculated to high accuracy at the CCSD(T)/cc-pVQZ level of ab initio theory and agree well with the experimental ones.     

Millimeter-wave spectrum of DCCCHO in the ground vibrational state

About 140 a- and b-type millimeter-wave transitions of propynal-d₁, DCCCHO, were measured in the ground vibrational state. The accurate rotational and centrifugal distortion constants were determined from the observed frequencies including the previous microwave measurements. Seven microwave transitions observed by infrared-microwave double resonance were also included in the analysis. The determined constants are A = 66778.016(12), B = 4463.8489(7), C = 4177.7950(7), Δ_J = 0.0015919(5), Δ_JK = −0.139214(13), Δ_K = 9.4328(18), δ_J = 0.0002885(4), δ_K = 0.03069(4), H_JK = −0.817(13) × 10⁻⁶, H_KJ = −9.62(4) × 10⁻⁶, H_K = 0.00255(8), h_J = 0.0047(3) × 10⁻⁶, in MHz.     

Far-infrared diffuse reflectance spectrum of kaolinite

Diffuse reflectance spectra of kaolinite have been obtained in the 100–700 cm⁻¹ region. Above 200 cm⁻¹, spectra were obtained for samples diluted in powdered polyethylene; for very low frequencies neat kaolinite was used. The observed frequencies are compared with existing IR transmission data, with Raman spectra and with the results of published normal coordinate calculations.     

Far-infrared self-broadening and pressure shift measurements of methyl cyanide

Pressure shifts and self-broadening parameters of the J=4342, J=4443, J=5655 and J=6867 sub-bands of the¹A₁ ground state of CH₃C¹⁴N up to K=10 were determined using the NIST tunable far-infrared (TuFIR) spectrometer. The pressure shift agrees well with theoretical predictions made using Anderson-Tsao-Curnutte theory. The self-broadening parameter shows the expected K depencence. However, the predictions are systematically too large for decreasing J. The influence of the TuFIR power spectrum on the derived experimental parameters was evaluated and a comparison was made between two-wave and three-wave mixing spectroscopy.     

Submillimeter rotational spectrum of formamide in the ground vibrational state

Radio Astronomy Institute, Academy of Sciences of the Ukrainian SSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 2, pp. 213–216, February, 1991.     

Far-infrared laser magnetic resonance spectrum of34S16O in X3Σ− state

The far-infrared laser magnetic resonance spectrum of³⁴S¹⁶O in the ground X³Σ^? state has been observed using five optically pumped laser lines as sources. The isotopic sulfur monoxide radical was produced by the reaction of oxygen gas with sulfur vaporized from an oven. The construction and design of such an oven have been discussed. A merged least squares fit of the earlier EPR and microwave results, and the present data yield better-determined molecular constants.     

Far-infrared spectrum and ring-puckering of 3-cyclopenten-1-one

The far-infrared spectrum of 3-cyclopenten-1-one in the vapor phase has been recorded and a broad absorption with a series of several Q branches was observed in the 80–120 cm^?1 region. This series of transition frequencies resulting from the ring-puckering vibration was fitted by the single minimum potential function V = 11.31 (Z⁴ + 12.56 Z²) cm^?1, which is characteristic of a planar ring structure. The origin of the potential function for this molecule and related molecules is discussed.