The Millimeter- and Submillimeter-Wave Spectrum of HC(3)N in the Ground and Vibrationally Excited States.

The pure rotational spectrum of the astrophysically very important linear molecule cyanoacetylene, HC(3)N, in the ground and vibrationally excited states has been studied in selected regions from 118 to 814 GHz using the Cologne terahertz spectrometer. Vibrational satellites appendant to the following vibrational states have been recorded and analyzed (v(4), v(5), v(6), v(7)): (0, 0, 0, 1), (0, 0, 0, 2), (0, 0, 1, 0), (0, 0, 1, 1), (1, 0, 0, 0), (1, 0, 0, 1), and the Fermi resonance systems (0, 1, 0, 0)/(0, 0, 0, 3) and (1, 0, 0, 2)/(0, 2, 0, 0)(0e). With the exception of the latter resonance system, all states have been fitted within experimental accuracy. This work provides improved rest frequencies for the astronomical community and may also be beneficial in the improvement of global fits. Copyright 2000 Academic Press.

The Millimeter- and Submillimeter-Wave Spectrum and the Dipole Moment of Ethylenimine.

The rotational spectrum of ethylenimine (aziridine, c-C(2)H(4)NH) has been investigated in selected regions from 118 to 950 GHz using the Cologne terahertz spectrometer. About 320 lines have been measured spanning the quantum numbers 2

The Rotational Spectra, Isotopically Independent Parameters, and Interatomic Potentials for the X(1)(2)Pi(3/2) and X(2)(2)Pi(1/2) States of BrO.

Observations of the rotational spectrum of BrO have been extended to include vibrational levels up to v = 8 in the X(1)(2)Pi(3/2) and v = 7 in the X(2)(2)Pi(1/2) states. The rotational spectra of isotopically enriched Br(18)O, X(1), v = 0, 1 and X(2), v = 0 have been observed as well. The spectra of all four isotopic species have been fit to a Hamiltonian in which the parameters have fixed isotopic ratios. An extensive set of isotopically independent parameters has been determined. Interatomic potentials have been derived for both the X(1) and X(2) states. The hyperfine constants and their vibrational dependencies have been determined more precisely and several of them have been determined for the first time. These are interpreted in terms of the electronic structure of the molecule. The isotope relations among the constants have provided a means of decorrelating the electron spin-rotation constant gamma from the fine-structure centrifugal distortion constant, A(D), and have allowed the first determination of an effective value for gamma. Copyright 2001 Academic Press.

Rotational Spectra of the Thiosulfeno Radical, HSS and DSS, between 0.3 and 0.9 THz.

The rotational spectra of the HSS and DSS radicals were studied in selected regions between 331 and 883 GHz. The radicals were produced by discharging a gaseous mixture of hydrogen (or deuterium) and hydrogen sulfide in the cell. The observation of the b-type Q-branch and R-branch lines with K(a) = 2-1 and 3-2 for HSS and DSS, respectively, as well as the a-type R-branch lines allowed the improvement and the determination of the molecular constants among them (in MHz) We have reevaluated the harmonic force field of HSS and the ground state average and approximate equilibrium structural parameters. For the latter, we obtained r(HS) = 135.23 pm, r(SS) = 196.03 pm, and angle = 101.74 degrees. These results are compared with those from previous and own quantum chemical calculations as well as with results of related molecules. Copyright 2000 Academic Press.

Submillimeter-Wave Spectroscopy of Phosphaalkynes: HCCCP, NCCP, HCP, and DCP.

The submillimeter-wave rotational spectra of the unstable phosphorus-bearing molecules HCCCP (phosphabutadiyne) and NCCP (C-cyanophosphaethyne) have been investigated in selected frequency regions between 490 and 815 GHz using the Cologne Terahertz Spectrometer. Both molecules were studied in their ground vibrational states. Additionally, vibrational satellites within the bending states v(4) = 1 and v(5) = 1 were recorded for NCCP. Furthermore, the ground state rotational spectra of the (13)C and (15)N isotopomers of NCCP were detected in natural abundance. The new measurements allowed us to evaluate the sextic centrifugal distortion constants for each isotopomer and vibrational state investigated. The pyrolysis reactions, through which HCCCP and NCCP were produced in situ, also yielded phosphaethyne, HCP, as a by-product. Some transitions of HCP and DCP were recorded in their ground vibrational states along with v(2) = 1 vibrational satellites of the former. Copyright 2001 Academic Press.

Terahertz Spectroscopy of the Amidogen Radical, NH2.

The rotational spectrum of the NH2 radical in its &Xtilde;2B1 ground vibronic state was investigated between 614 and 1003 GHz. One hundred fifty-nine newly observed lines (188 hyperfine components) of six rotational transitions with 0

The Rotational Spectrum of SO(2) and the Determination of the Hyperfine Constants and Nuclear Magnetic Shielding Tensors of (33)SO(2) and SO(17)O.

Precise frequencies for the 1(11)-2(02) transition of (33)SO(2) and SO(17)O in natural isotopic abundance have been obtained near 12 GHz by microwave Fourier transform spectroscopy in order to yield improved hyperfine constants. Nuclear spin-rotation coupling constants have been determined experimentally for (33)SO(2) for the first time. The spin-rotation constants have been used to derive nuclear magnetic shielding parameters. These parameters are compared with values for the isoelectronic O(3) molecule. The transition mentioned above was also measured for (32)SO(2), (34)SO(2), SO(18)O, and vibrationally excited (v(2) = 1) (32)SO(2). For (33)SO(2), some transitions with large hyperfine splitting were also recorded in the millimeter-wave region. Continuing our investigations of the rotational spectra of SO(2) in the submillimeter region, several transitions of SO(17)O have been recorded with the Cologne terahertz spectrometer between 540 and 840 GHz with J and K(a) up to 63 and 16, respectively. Transitions with high K(a), up to 28, have been recorded with the JPL laser sideband spectrometer between 1.8 and 3.2 THz. Copyright 2000 Academic Press.