K. V. L. N. Sastry

The millimeter wave spectra of isocyanic and isothiocyanic acids

Abstract An investigation of the mm-wave rotational spectra of the very slightly asymmetric tops HNCS, DNCS, HNCO and DNCO has been carried out in the frequency range 80 000–190 000 Mc/sec. Several R -branch, a -type, transitions were observed for each molecule and the rotational constants A 0 , B 0 , and C 0 were determined for the four species containing the most abundant isotopes of N, C, O, or S. B 0 and C 0 were also found for HNCS 34 . The centrifugal distortion constant D J was obtained for each abundant form. The constants are HNCS: A 0 = 1 483 000 ± 167 000 Mc/sec, B 0 = 5883.42 ± 0.02 Mc/sec, C 0 = 5845.62 ± 0.02 Mc/sec, D j = 1.17 ± 0.05 Kc/sec; DNCS: A 0 = 723 400 ± 25 000 Mc/sec, B 0 = 5500.51 ± 0.05 Mc/sec, C 0 = 5445.26 ± 0.05 Mc/sec, D j = 1.22 ± 0.31 Kc/sec; HNCS 34 : B 0 = 5744.81 ± 0.20 Mc/sec, C 0 = 5708.73 ± 0.20 Mc/sec; HNCO: A 0 = 956 400 ± 50 000 Mc/sec, B 0 = 11 071.02 ± 0.05 Mc/sec, C 0 = 10 910.58 ± 0.05 Mc/sec, D j = 3.5 ± 0.5 Kc/sec; DNCO: A 0 = 534 500 ± 70 000 Mc/sec, B 0 = 10 313.61 ± 0.05 Mc/sec, C 0 = 10 079.67 ± 0.05 Mc/sec, D j = 2.9 ± 0.5 Kc/sec. The centrifugal distortion K -pattern is different in character for each of the four molecules. Agreement between calculation and experiment is obtained for HNCO and DNCO with the additional constants; HNCO; D JK = +837 Kc/sec, H JJK = −0.056 Kc/sec, H JKK = +2.81 Kc/sec. DNCO: D JK = −227.1 Kc/sec, H JJK = +0.15 Kc/sec, H JKK = −5.61 Kc/sec, H JJJ = 0, utilizing the expression given by Costain. This expression gives a poor fit for DNCS and no fit for HNCS, and at present no treatment has been found to fit or explain satisfactorily the K -patterns for these two molecules. An improved molecular structure has been calculated for HNCS the structural parameters being revised to r (HN) = 0.988 7 ± 0.003 A, r (NC) = 1.216 4 ± 0.007 A, r (CS) = 1.560 5 ± 0.003 A A number of lines due to rotational transitions of vibrationally excited molecules were also observed and are assigned to the states v 5 = 1 and v 6 = 1 for HNCS and HNCO and probably, in addition, v 4 = 1 for DNCS.

Millimeter Wave Spectroscopy of Unstable Molecular Species. I. Carbon Monosulfide

The carbon monosulfide species CS32 and CS34 are investigated with a millimeter wave spectrometer designed for the study of short‐lived molecules in the frequency range from 60 000 to 300 000 Mc/sec. Spectroscopic constants obtained are:           CS32          CS34B0=24 495.592±0.006 Mc/secB0=24 103.554±0.006 Mc/secBe=24 584.367±0.006 Mc/secDe=0.03979±0.0017 Mc/secαe=117.550±0.012 Mc/secHe=0.0625±0.009 kc/secDe=0.04285±0.00166 Mc/secHe=0.0653±0.0085 kc/sec The spectrometer is described. Its sensitivity has been estimated to be the order of 10—5 to 10—6 cm—1.

The laboratory millimeter and submillimeter spectrum of HCO

The rotational absorption frequencies of 68 new lines from the HCO radical in its ground electronic state have been measured in the millimeter and submillimeter spectral region. The large zero‐field data set acquired has allowed the complex spectrum of this light asymmetric rotor with unpaired electronic spin and magnetic hyperfine interactions to be completely analyzed to within experimental accuracy (<0.1 MHz) for the first time. The wide range of states observed provides a highly accurate map of the rotational frequencies of the formyl radical, which should enable the abundance and excitation of interstellar HCO to be examined in detail.

Millimeter Wave Spectroscopy of Unstable Molecular Species. II. Sulfur Monoxide

Several spectral transitions of the gaseous free radical SO have been observed in the millimeter wave region. Analysis of the observed lines confirms that the molecule has a 3Σ ground state and leads to the rotational constants B0=21 523.75 Mc/sec and D0=0.0334 Mc/sec, also to the magnetic coupling constants λ=158 209.4 Mc/sec and γ=—164.52 Mc/sec. The assignments and analysis are confirmed by a close fitting, within approximately 1 Mc/sec, of all measured and calculated frequencies, and by the Zeeman effect which is measured and analyzed for several transitions.

Millimeter and submillimeter spectra of HCO/+/ and DCO/+/

The J = 0-1 transitions of six different isotopic forms of the HCO(+) molecular ion, which were investigated by Woods et al. (1975), are considered. The extension of this work into the shorter millimeter and submillimeter region is reported here, as is the measurement of these spectra through J = 4-5 for HCO(+) and J = 5-6 for DCO(+). It is noted that these measurements can be used to determine accurate rotational constants and rest frequencies for these astrophysically important species. Tables listing the observed rotational constants and spectral constants of HCO(+) and DCO(+) are included.

Microwave and millimeter wave spectra of hydrazoic acid

Abstract Five rotational transitions have been recorded for each of the abundant species of hydrazoic acid and hydrazoic acid-d. Both molecules have normal centrifugal distortion behavior. The spectroscopic constants derived from the measurements are HN 3 −A 0 = 615,600 ± 7000 Mc/sec, B 0 = 12,034.15 ± 0.09 Mc/sec, C 0 = 11,781.51 ± 0.09 Mc/sec, D JK = 787.8 ± 5.4 kc/sec, D J = 5.09 ± 0.54 kc/sec, H JKK = −1.13 ± 0.15 kc/sec, H JJK - 0.03 ± 0.03 kc/sec. DN 3 −A 0 = 351,500 ± 7000 Mc/sec, B 0 = 1,350.23 ± 0.05 Mc/sec, C 0 = 10,965.48 ± 0.05 Mc/sec, D JK = 442.6 ± 2.4 kc/sec, D J = 4.22 ± 0.17 kc/sec, H JKK = − 0.21 ± 0.08 kc/sec, H JJK = − 0.03 ± 0.02 kc/sec. An important part of the study was a reinvestigation of the J = 0 → 1 transition of HN 3 which gave eq aa Q = 4.65 ± 0.25Mc/sec for the NH nitrogen N 14 nucleus.

The millimeter wave spectra of NaH and NaD

Utilizing a glow discharge absorption cell, we have detected the v = 0, 1, 2, and 3, J = 0→1 transitions of NaH and the v = 0, 1, 2, and 3, J = 1→2 and v = 0, J = 2→3 transitions of NaD in the millimeter and submillimeter regions of the spectrum. The derived Dunham constants (MHz) are A significant breakdown of the Born–Oppenheimer approximation has been observed.

The laboratory millimeter- and submillimeter-wave spectrum of the first two excited torsional states of (C-13)H3OH

The rotational-torsional spectrum of (C-13)H/sub 3/OH is presented in both the symmetric and degenerate substates of the first two excited torsional states. Of the new transitions reported, 122 lines are from the v(t) = 1 torsional state and 110 lines are from the v(t) = 2 torsional state, and all are confined to the rotational quantum number J = 8 or less. The data are combined with previously reported millimeter and submillimeter data for the v(t) = 0 torsional state and 44 previously measured excited torsional state lines to form a global data set of 596 transitions, which is analyzed and fitted using an extended internal axis method. The fit results in an overall rms deviation of 1.98 MHz. The spectral constants generated by the fit are used to predict an additional 123 lines of (C-13)H/sub 3/OH in the v(t) = 1,2 excited torsional states with frequencies up to 612 GHz and rotational quantum number J = 11 or less. 24 references.

Laboratory millimeter and submillimeter spectra of HNO and DNO

The identification of interstellar molecular species via the detection of one spectral line has recently become subject to close scrutiny. The radical HNO falls into the class of interstellar molecules identified in this manner. To corroborate this identification, observation of additional spectral lines is necessary. In this paper, laboratory millimeter and submillimeter wave spectra of both HNO and DNO are reported in the frequency region 150-500 GHz. Based on these spectral line measurements, models for HNO and DNO have been constructed to yield accurate frequencies for all rotational transitions of these species below 500 GHz involving J values smaller than 10. The spectral lines can be utilized by radio astronomers to confirm the identification of interstellar HNO and to search for interstellar DNO.