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.     

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.     

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     

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.     

Microwave spectra of the ground vibrational state of formaldehyde substituted with O and O

Pure rotational transitions in the ground vibrational state have been measured for H₂¹²C¹⁸O, H₂¹²C¹⁷O, H₂¹³C¹⁸O, and H₂¹³C¹⁷O in the frequency region 8–75 GHz. These have included both Q- and R-branch transitions, and have permitted accurate evaluation of rotational constants and several quartic centrifugal distortion constants for each species. These in turn have permitted the prediction of several transitions of possible use in radioastronomy.     

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.     

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.     

Microwave spectra of the ground vibrational state of formaldehyde substituted with 17O and 18O

Pure rotational transitions in the ground vibrational state have been measured for H₂¹²C¹⁸O, H₂¹²C¹⁷O, H₂¹³C¹⁸O, and H₂¹³C¹⁷O in the frequency region 8–75 GHz. These have included both Q- and R-branch transitions, and have permitted accurate evaluation of rotational constants and several quartic centrifugal distortion constants for each species. These in turn have permitted the prediction of several transitions of possible use in radioastronomy.     

Determination of the ground state rotational constants for formaldehyde: H212CO and H213CO

The two isotopic species CH₂DCOOH and CH₂DCOOD of acetic acid have been investigated with microwave spectroscopy in order to determine the equilibrium configuration of the methyl group, which was found to be eclipsed with respect to the carbonyl group. Centrifugal distortion constants free from internal rotation effects have been determined. A r_s structure for the four hydrogens and a partial r₀ structure for the whole molecule are given.     

The b-type rotational transitions of HNCO in the lowest excited vibrational state

In the microwave and millimeter wave spectra of HNCO, the b-type transitions between the K_a = 0 and 1 levels in the lowest excited vibrational state have been observed. Because of strong a-type Coriolis resonances among the three bending excited states the energy difference between the levels for K_a = 0 and 1 is much smaller in the lowest excited state than in the ground state. The subband origin of these b-type transitions has been found in the millimeter wave region at 275 697.309 MHz (9.1963 cm^?1). The effect of the Coriolis resonances is discussed in relation to the molecular quasi-linearity and is compared with the case of HNCS.     

Determination of relaxation times of ground electronic state vibrational levels of mixed molecular crystals

The stimulated emission spectra of mixed molecular crystals were investigated with the Nd glass lasser third harmonic excitation at 4.2 K. Napthalene crystals doped with β-naphthyl-n-biphenylyl ethylene and dibenzyl doped with naphthacene in various concentrations were studied. Relaxation times of the ground state vibrational levels in mixed molecules were obtained by use of the dependence of stimulated emission intensity upon excitation energy for naphthacene in dibenzyl τ₁ of the vibrational level at 317 cm^-1 was ～ 3 × 10^-9 s; for β-naphthyl-n-biphenylyl ethylene in naphthalene τ₁ of the 1629 cm^-1 vibrational level was ～ 10^-10 s.     

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.     

Pure rotational Q-branch spectrum of silane-28Si in the vibrational ground state observed by microwave Fourier transform spectroscopy

A pulsed microwave Fourier transform (MWFT) spectrometer operating in the 8- to 18-GHz frequency range has been used to observe pure rotational Q-branch microwave transitions of silane-²⁸Si. The 49 measured transitions are of all three parity-allowed types A₁-A₂, E-E, and F₁-F₂, and cover the range 13 ≤ J ≤ 25. A set of refined tensorial centrifugal distortion constants D_T, H_4T, H_6T, L_4T, L_6T, and L_8T has been determined by a least-squares fit from a total of 70 measurements. The fit included the 49 MWFT measurements of this work, 11 transitions observed with Stark spectroscopy, nine infrared-radio frequency double-resonance measurements, and one zero-field splitting determined from an avoided-crossing molecular-beam experiment.     

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.     

g-factors of the ground state rotational band of158Dy

Theg-factors of the four lowest states of the ground state rotational band of¹⁵⁸Dy have been determined asg(2 ₁ ⁺ )=+0.362(23),g(4 ₁ ^su+ )=+0.340(20),g(6 ₁ ^su+ )=+0.207(36) andg(8 ₁ ^su+ )=+0.21(11). Theg-factors of the 2⁺ and 4⁺ states were measured by the IPAC method with radioactive samples of 2.4 h¹⁵⁸Er in external magnetic fields. To investigate the higher states, for the first time an on-line γ—γ IPAC experiment was performed with the reaction¹⁵⁶Gd(α, 2n)¹⁵⁸Dy by use of the static hyperfine field of DyGd.     

The influence of rotational states on the kinetic of vibrational levels of CO2. The method of rotational weight function

We study the influence of rotational states on the kinetics of vibrational levels of CO₂ using a numerical method. Spontaneous emission is considered to be the mechanism causing transitions between rotational-vibrational states. It is shown that results obtained in the generally assumed vibrational approximation can differ by factors of 5–10 from the results where rotational states are taken into account. We propose a method of rotational weight functions which takes into account rotational states in the calculation of the kinetics of vibrational levels. We also find numerical values of these weight functions and show that the results obtained differ from the exact ones by 1–3%.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 88–92, January, 1986.