Observation of the 43Σ+ g , 33Π g , 23Δ g , and b 3Π u states of 39K2 by perturbation facilitated optical-optical double resonance spectroscopy J. Chem. Phys. 102, 6646 (1995); 10.1063/1.469137 Laser spectroscopy of the A2Π-X2Σ+ transition of SrOH: Deperturbation analysis of Kresonance in the v 2=1 level of the A2Π state Determination of the internal state distribution of NO(X 2Π) produced in the O(3 P)+NH(X 3Σ−) reaction J. Chem. Phys. 97, 180 (1992); 10.1063/1.463606 Rotation-vibration analysis by finite difference perturbation technique. Application to 1Σ+ state of NHThe v = 1-0 vibration-rotation transitions in the X 2n and a 41; -states as well as those between the two electronic states were observed with a difference frequency laser as a radiation source. The two electronic states (X 2n and a 41; -) lie close together and interact each other strongly through the spin-orbit coupling. A merged least-squares fit was carried out with the present infrared transition wave numbers, some of the previous optical term values, and the recent far-infrared rotational transition frequencies to determine the spectroscopic parameters precisely. The equilibrium internuclear distance was obtained to be 1.0692 ± 0.0002 and 1.0924 ± 0.0001 A for the X and a states, respectively. The A-type doubling transition frequencies were calculated for several of the lowest J states with the molecular constants obtained and the hyperfine coupling constants determined from the far-infrared transitions.

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The high-resolution spectrum of the ν4 fundamental band of NH3D+ has been observed in absorption in a hollow-cathode discharge with a difference-frequency laser system. The molecular constants have been determined through a least squares fit of the observed transition wave numbers to an effective Hamiltonian. The equilibrium rotational constant is estimated to be 4.438 ± 0.027 cm−1, from which the equilibrium N—H bond length is calculated to be 1.021 ± 0.003 Å. Some low-lying rotational transition frequencies in the ground state are calculated to assist in the search for pure rotational transitions in the laboratory and in interstellar space.

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The polarized absorption spectra in the 280–1100 mμ region have been observed for the single crystals of eight molecular compounds which involve N,N,N′,N′-tetramethylbenzidine and benzidine as the electron donor and p-chloranil, TCNQ, 1,3,5-trinitrobenzene, and p-benzoquinone as the electron acceptor. The donor and acceptor molecules are not in the ionic states in the ground states of these molecular compounds, in spite of the low ionization potentials of tetramethylbenzidine and benzidine. The observed spectra are composed of absorption bands associated with intramolecular transitions in the constituent molecules and those associated with the charge transfer from the donor to the acceptor. It was found that the polarization of the second charge transfer band is almost perpendicular to that of the first one in the case of chloranil and TCNQ, compounds of benzidine and tetramethylbenzidine. In other cases, the first and second charge transfer bands were confirmed to be polarized nearly parallel to each other as in a usual charge transfer molecular compound.

The rotational transitions of NCS have been observed in the 1 to 3 mm wavelength region in a hollow cathode discharge in a gas mixture of CS2 (∼1 mTorr) and N2 (∼30 mTorr). The molecular constants in the ground state are determined by fitting the observed frequencies to the standard Hamiltonian for 2Π states. The accuracy of the molecular constants are greatly improved compared with the values obtained from the optical data. The lines in the excited vibronic states have also been observed. The analysis including those excited state lines is in progress and the results will be published separately.

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