Inversion of the Ka = 0 and 1 rotational levels in the lowest excited vibrational state of HNCS

Fairly strong, regularly spaced absorption lines have been observed in the microwave spectrum of HNCS and assigned to b-type, K_a = 0 ← 1, Q-branch transitions arising from molecules in the lowest excited vibrational state. The Fortrat diagram of these lines has the appearance of a c-type Q branch, which is impossible in HNCS because of its symmetry. This anomalous b-type Q-branch spectrum is caused by strong a-type Coriolis interactions among the three low-lying bending modes; the K_a = 1 levels of the lowest excited vibrational state are perturbed and shifted lower in energy than the K_a = 0 levels for each J. This interpretation has been confirmed by the observation of P- and R-branch transitions associated with this Q branch. The band origin has been determined to be ?40 104.287 MHz (?1.3377 cm^?1). The inversion of the K_a = 0 and 1 energy levels is consistent with the interpretation of HNCS as a quasi-linear molecule.     

The a-type rotational spectrum of isocyanic acid,HNCO, in the excited bending states

Rotational transitions of HNCO in the v₄ = 1, v₅ = 1, and v₆ = 1 vibrational states have been measured. The assignment of the a-type ^qR_K and ^qQ₁ branches has been made with the help of a qualitative discussion of the vibration-rotation interactions. Effective rotational and centrifugal distortion constants have been determined precisely for each vibrational K_a-rotational state, up to K_a = 4 for the lowest excited state and K_a = 3 for the other two excited states. The K_a dependence of the effective rotational constants B and D was observed to be quite anomalous for some of the transitions because of the a-type Coriolis interactions and accidental b-type Coriolis resonances. From a discussion of the selection rules and the effect on B and D of the interactions, the first excited state of the out-of-plane vibration, ν₆, has been assigned definitely to the second lowest excited vibrational state of HNCO.     

The rotational levels of the ground vibrational state of formaldehyde

A variational procedure for rovibrational energy levels and wavefunctions of centrally connected tetra-atomic molecules is extended to include high rotational states, and in particular, J ? 10 levels for the vibrational ground state of formaldehyde. It is very important to do this because it has made possible the calculation of the usual rotational spectroscopic constants which correspond to the forcefield and geometry. A direct comparison with the ‘observed’ spectroscopic constants is therefore possible. The geometry and forcefield are refined against 65 J = 0 levels of H₂CO, 6 J = 0 levels of D₂CO, 42 J = 1, 70 J = 2 and 98 J = 3 levels of the ground and fundamentals of H₂CO and D₂CO, using an iterative scheme. The mean absolute error of the J = 0 levels is 1·10 cm^?1 and that for J ≠ 0 is 0·005 cm^?1, and the predicted geometry is CH = 1·10064 Å, CO = 1·20296 Å and HCO = 121·648°. Finally, the rotational constants A, B, and C for the ground state are 281956, 38846 and 34003 MHz, compared with the observed values 281971, 38836, and 34002 MHz. The centrifugal distortion constants Δ_J , Δ_JK , Δ_K and δ_J , are 77, 1275, 18113 and 11 kHz compared with 75, 1291, 19422 and 10 kHz. These results underline the accuracy of the new quartic forcefield.     

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.     

The rotational spectrum of acrylonitrile in excited states of the two low-frequency CCN bending vibrational modes

The strongest vibrational satellites in the rotational spectrum of acrylonitrile have been assigned and frequencies of μ_a- and μ_b-type transitions in the frequency range 27–184 GHz are reported for the first two excited states in the lowest frequency in-plane CCN bending vibrational mode and the first excited state in the out-of-plane CCN bending mode. The values of the rotational constants, the quartic and sextic centrifugal distortion constants, and one octic centrifugal distortion constant are determined for each of these states. Less extensive results are also presented for the third quantum of the in-plane bend. The data set for the ground state has been extended by a number of new measurements and the improved ground state constants are used in a discussion of changes in rotational and centrifugal distortion constants with vibrational state where all constants associated with P_zⁿ and P²P_z⁽ⁿ⁻²⁾ terms in the Hamiltonian are found to reflect the common origin of the two CCN bends.     

Microwave spectrum of the molecular oxygen in the excited vibrational state

The fine-structure spectra of ¹⁶O₂ in the first excited vibrational state have been observed at room temperature with a double-modulation spectrometer. The spectra of an isotopic species ¹⁶O¹⁸O in the ground state are also observed in natural isotopic abundance. Revised energy formulas, which are derived as a slight extension of Tinkham and Strandberg's treatment, are used in the analyses, and much more accurate equilibrium molecular constants are determined; λ′_e = 59 429.08 ± 0.11 MHz, μ_e = ?252.265 ± 0.011 MHz, B_e = 43 336.2 ± 1.5 MHz, and $\text{r}{}_{\mathrm{e}}\text{= 1.20748 ± 0.00005}\text{A}\text{?}$.     

A rotational Hamiltonian for the ground vibrational state of hydrazine

A Hamiltonian matrix suitable for fitting rotational energy levels of the hydrazine molecule in its ground vibrational and electronic states was obtained. This matrix is of dimension 16 × 16, where the 16 functions labeling the rows and columns consist of the two members of a near-prolate asymmetric rotor doublet (with given | K_a |) for the eight different, but chemically equivalent, conformers which the molecule can reach by various combinations of -NH₂ inversion at either end of the molecule, and internal rotation about the NN bond. The matrix is derived in a phenomenological fashion, by applying group theoretical arguments to a model in which tunneling among the various frameworks is assumed to be very slow compared with the vibrational frequencies. A comprehensive treatment of the large-amplitude vibrational potential surfaces and associated tunneling pathways has not been carried out, nor have quartic (J⁴) centrifugal distortion effects been considered in a systematic fashion. Preliminary fits indicate that the model developed can be used to fit the hydrazine microwave data in a consistent fashion, and a full treatment of such data has been undertaken.     

Selecting molecules in the vibrational and rotational ground state by deflection

A beam of diatomic molecules scattered off a standing wave laser mode splits according to the rovibrational quantum state of the molecules. Our numerical calculation shows that single state resolution can be achieved by properly tuned, monochromatic light. The proposed scheme allows for selecting non-vibrating and non-rotating molecules from a thermal beam, implementing a laser Maxwell's demon to prepare a rovibrationally cold molecular ensemble. Received 23 August 2000 and Received in final form 17 November 2000     

The millimeter-wave rotational spectrum of CF3CCD in the excited vibrational state v10=2

The millimetre-wave rotational spectra of the excited vibrational state v₁₀=2 of the symmetric top molecule, CF₃CCD, have been recorded for J^′′=12 up to J^′′=25. The l=±2 and l=0 series have been assigned and the spectra analysed to give rotational parameters including x_ll=7716.975 MHz. The main interactions between states of different l are the r_t(2,−1)=0.158 MHz and q_t⁺(2,2)=3.308 MHz. Two type of l-resonance are identified, one of which is due to an avoided crossing between the l=0 and l=+2 series. The spectra are qualitatively similar to the corresponding ones of CF₃CCH.     

Millimeter and submillimeter wave rotational spectrum of pyridine in the ground and excited vibrational states

The pure rotational spectra of the ground and five excited vibrational states of pyridine were measured, assigned and fit in the 75-110 and 260-370 GHz frequency bands. An improved set of spectroscopic constants was obtained for the ground state, and all the rotational and quartic centrifugal distortion constants were obtained for the excited vibrational states.     

Submillimeter rotational spectrum of the formamide molecule: Ground and first excited vibrational states

The results of a study of the submillimeter rotational spectrum of formamide in states v_T=0 and 1 at frequencies of 290–500 GHz are presented. More than 300 transition frequencies are identified. Watson Hamiltonian constants are obtained for both states.Radio-Astronomy Institute, Academy of Sciences of Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 2, pp. 259–264, February, 1994.     

Millimeter wave rotational spectrum of deuterofulminic acid,DCNO, in excited vibrational states

Rotational transitions of DCNO in the vibrational states 00002, 00003, 00020, and 00011 have been measured and analyzed. These results complete the presentation of assigned millimeter wave transitions of DCNO.The analysis of rotational l-type resonance in the 00002 and 00020 states is more satisfactory in the case of DCNO than in that of HCNO due to the absence of accidental resonances. The values obtained for the vibrational anharmonicity constant g₅₅ for 00002 and 00003 agree within experimental error with those found from the vibrational spectrum.An ambiguity in the assignment of the symmetry of the transitions in the four components of the 00011 vibrational state is discussed.     

High resolution study of the six lowest doubly excited vibrational states of PH2D

The five lowest doubly excited deformational vibrational bands ν₄ + ν₆, 2ν₆, ν₃ + ν₄, ν₃ + ν₆, and 2ν₃ of PH₂D have been recorded for the first time using a Bruker 120 HR interferometer with a resolution 0.0033 cm⁻¹ and analysed. Some transitions belonging to a very weak band 2ν₄ have been also assigned. From the fit 24 and 86, respectively, diagonal and resonance interaction parameters were obtained which reproduce 1089 upper energy levels obtained from more than 4600 assigned transitions with the rms deviation of 0.00059 cm⁻¹.     

Pure rotational spectrum of cyanopropyne in the v12 = 1 vibrational state

The micoowave and millimeter-wave spectrum of cyanopropyne, CH₃CCCN, in the lowest excited vibrational state, v₁₂ = 1 (E), has been observed in the frequency range from 8 to 220 GHz. The measurements up to the J = 53−52 transitions allowed us to determine the Coriolis coupling term and the l-type interaction term very precisely in addition to some of the sextic centrifugal terms. The contribution of the r-type interaction (Δk = ±1, Δl = ±2) has been found to be correlated with that of η_J, a centrifugal correction term to the first-order Coriolis interaction.     

Modeling of hydrogen ground state rotational and vibrational temperatures in kinetic plasmas

A dipole-quadrupole electron-impact excitation model, consistent with molecular symmetry rules, is presented to fit ro-vibronic spectra of the hydrogen Fulcher-α Q-branch line emissions for passively measuring the rotational temperature of hydrogen neutral molecules in kinetic plasmas with the coronal equilibrium approximation. A quasi-rotational temperature and quadrupole contribution factor are adjustable parameters in the model. Quadrupole excitation is possible due to a violation of the 1st Born approximation for low to medium energy electrons (up to several hundred eV). The Born-Oppenheimer and Franck-Condon approximations are implicitly shown to hold. A quadrupole contribution of 10% is shown to fit experimental data at several temperatures from different experiments with electron energies from several to 100 eV. A convenient chart is produced to graphically determine the vibrational temperature of the hydrogen molecules from diagonal band intensities, if the ground state distribution is Boltzmann. Hydrogen vibrational modes are long-lived, surviving up to thousands of wall collisions, consistent with multiple other molecular dynamics computational results. The importance of inter-molecular collisions during a plasma pulse is also discussed.     

The lowest singlet state of dibenzofuran

The vapor absorption of dibenzofuran has been reexamined, and the spectrum and lifetime of the vapor fluorescence have been measured. Also measured were the polarized absorption in durene host and the depolarized absorption, fluorescence, and phosphorescence in cyclododecane host at 4 K. The fluoresecent state is that corresponding to the 3000 Å absorption in all media, and no evidence was found for a weak transition at 3175 Å as reported by Pinkham and Wait. The mixed crystal spectra are heavily perturbed, but from the polarizations observed in durene the 3000 Å transition is assigned as ${}^1\text{B}{}_2\text{←}{}^1\text{A}{}_1$ (long axis polarized).