Quadrupole hyperfine structure of the rotational spectrum of aminoacetonitrile

From high-resolution studies of the microwave spectrum of aminoacetonitrile we have established the quadrupole coupling constants of both nitrogen atoms in the molecule. They are χ_aa = ?2.77 (0.04) MHz, χ_bb = 1.20 (0.09) MHz for the amino nitrogen, χ_aa = ?3.48 (0.03) MHz, χ_bb = 1.50 (0.06) MHz for the nitrile nitrogen. Improved values for rotational constants and centrifugal distortion constants also emerge from the present spectral analysis.     

Microwave spectrum of PHD: hyperfine structure

The rotational spectrum of the monodeuterated PH₂ radical was studied using a source-modulated submillimeter-wave spectrometer. The PHD radical was generated in a free space absorption cell by a dc-glow discharge in a gas mixture of PH₃ and D₂. Six a-type and 20 b-type rotational transitions were observed in the frequency region of 170-670 GHz. Hyperfine structure due to the deuterium nucleus was resolved only in the rotational transitions of 1₁₁-0₀₀ and 1₁₀-1₀₁ and in the low F₂ components of N=2-1 transitions. A total of 219 spectral lines were measured of which 145 were analyzed by least-squares methods. These yielded 34 precise molecular constants including the hyperfine coupling constants of phosphorus, hydrogen, and deuterium. The principal axes and principal values of the magnetic dipole coupling tensors of hydrogen in PH₂ and deuterium in PD₂ were derived from the observed values of PHD, PH₂ and PD₂. The principal axis of the hydrogen magnetic dipole coupling tensor in PH₂ makes an angle of 2.29° with the PH bond and its T_σ and T_⊥ principal values are determined to be 12.93 and −18.39 MHz, respectively.     

The rotational spectrum and hyperfine structure of arsenic monophosphide, AsP

Arsenic monophosphide has been prepared by laser ablation of arsenic in the presence of PH₃. The J = 2-1 and 1-0 transitions in both the ground and first excited vibrational states have been measured with a cavity pulsed jet Fourier-transform microwave spectrometer. An improved equilibrium internuclear distance (r_e) has been obtained. Hyperfine structure in the rotational spectrum of AsP has been resolved and has led to the first determinations of the As nuclear quadrupole coupling constant and both nuclear spin-rotation constants. The data enable the electronic structure of AsP to be compared with those of other mixed Group 15 diatomic molecules.     

The magnetic hyperfine structure in the rotational spectrum of H2CNH

The hyperfine structure in the ground-state rotational spectrum of methanimine was studied in the frequency range of 64-172 GHz by means of the Lamb-dip technique. This allowed to resolve, in some hyperfine components due to the ¹⁴N nucleus, doublets separated by only some tenth of kHz. We explain the splittings as due to magnetic interactions of the three protons with their molecular environment. The analysis of the experimental spectrum has been guided by quantum-chemical calculations of the hyperfine parameters.     

Microwave spectrum of C methyl iodide

The results of reinvestigation of millimeter and submillimeter-wave spectrum of ¹³CH₃I molecule are reported. Microwave spectrum records were carried out in the frequency range 50-250 GHz and 280-330 GHz. For several series of rotational transitions the accuracy of measurements was improved by an order of magnitude. On the basis of large amount of experimental data (about 800 rotational transitions) for the first time the most complete set of molecular constants was obtained. Also for most of parameters the estimation accuracies were improved by several orders of magnitude.     

Microwave spectrum, tunneling motions, and quadrupole coupling hyperfine structure of ethylene diamine

New transitions are measured in the microwave spectrum of two conformers of the non-rigid ethylene diamine (CH₂NH₂-CH₂NH₂) molecule using both molecular beam Fourier transform and stark modulation spectroscopy. Ab initio calculations are carried out to obtain geometries and energies for several stationary points of the potential energy surface and to gain quantitative information on the tunneling paths along which the molecule tunnels. The microwave data are reproduced using an IAM-like approach which accounts for the rotational dependence of the tunneling splitting corresponding to the interconversion large amplitude motion. For one of the conformers, the results of this analysis are consistent with the ones obtained through ab initio calculations. Hyperfine patterns are analyzed with the help of a theoretical approach accounting for the large amplitude motion effects and for hyperfine matrix elements within and between tunneling sublevels.     

Microwave spectrum and rotational isomerism in isopropyl mercaptan

A microwave investigation of isopropyl mercaptan has established the existence of both trans and gauche conformers, the trans being more stable by 57 cal mole^?1. Stark effect measurements give the dipole moments as 1.61 ± 0.2 D for the trans and 1.53 ± 0.2 D for the gauche species. The spectra of the isotopic species (CH₃)₂CH³²SD, (CH₃)₂CH³⁴SH, and (CH₃)₂CH³⁴SD of the trans form have also been analyzed, providing a limited amount of structural data.The rotational spectrum of the gauche isomer is noticeably influenced by inversion. Interactions between energy levels in the two lowest inversion states have been satisfactorily accounted for in terms of rotational constants, coupling parameters (G_a and G_c), and ΔE₀, the inversion level splitting. ΔE₀ is found to be 562.4 MHz for the ground state of (CH₃)₂CHSH and 10.0 MHz for (CH₃)₂CHSD. A value of 1.98 kcal mole^?1 has been calculated for the barrier to internal rotation of the -SH group in terms of a V₃ potential.     

钕离子同位素移位和超精细结构光谱

原子光谱中,同位素移位和超精细结构光谱是少数几个能够将原子物理和原子核物理这两个不同的物理分支联系起来的课题之一.利用共线快离子束-激光光谱学方法测量了单电荷态钕离子4f45d6G3/2→(26041)°5/2跃迁(波长577.21 nm)的共振光谱,得到了所有7个稳定同位素(A=142～146,148,150)之间的能量移位和2个奇同位素(A=143,145)的超精细结构光谱.     

Fine and hyperfine structure in the atomic spectrum of niobium

A parametric analysis of the fine and the magnetic dipole hyperfine structure for the three configurations of odd parity 4d³5s5p, 4d⁴5p and 4d²5s²5p was performed. Effective one-electron parameters were determined and theoretical predictions are given for the magnetic dipole hyperfine structure constants A for the levels of these three configurations. Additionally, 12 new energy levels could be found, four of odd and eight of even parity, by re-analysing data for experimental wavelengths of Nb.     

Reinvestigation of the quadrupole hyperfine structure in rotational spectra of chloroiodomethane

The b-type Q-branch transitions of chloroiodomethane were remeasured and the quadrupole hyperfine structures were reinvestigated by a new method to improve the discrepancies in the hyperfine spectra observed and calculated in a previous work. The χ values of the off-diagonal element of ³⁵Cl and ³⁷Cl were determined. The nuclear quadrupole coupling constants were revised to be χ_aa = −1421.9 ± 1.9, χ_bb = 392.6 ± 1.0, χ_cc = 1029.3 ± 2.1, and {χ_ab} = 1174.9 ± 1.7 MHz of iodine; χ_aa = −31.1 ± 1.1, χ_bb = −9.0 ± 0.6, χ_cc = 40.1 ± 1.2, and {χ_ab} = 53.6 ± 4.2 MHz of ³⁵Cl for ³⁵Cl species; χ_aa = −1418.4 ± 2.5, χ_bb = 386.5 ± 2.7, χ_cc = 1031.9 ± 3.6, and {χ_ab} = 1181.8 ± 1.7 MHz of iodine; and χ_aa = −21.1 ± 1.7, χ_bb = −8.5 ± 0.9, χ_cc = 29.6 ± 1.9, and {χ_ab} = 34.6 ± 1.4 MHz of ³⁷Cl for ³⁷Cl species, respectively.     

Microwave spectrum of the32S17O radical. Magnetic hyperfine structure and quadrupole coupling constants

Summary The millimetre wave spectrum of the³²S¹⁷O free radical has been observed and analysed. The fine- and hyperfine-structure parameters have been determined. Ther ^s andr ^m structures have been also determined.

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Riassunto è stato osservato ed analizzato lo spettro millimetrico del radicale libero³²S¹⁷O. Sono stati determinati i parametri di struttura fine ed iperfine e le strutturer ^s er ^m.

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Резюме Наблюдался д проведен анализ спектра миллиметровых волн свободного радикала³²З¹⁷О. Определены параметры тонкой и сверхтонкой структуры. Также определены структурыr ^s иr ^m.

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To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.

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The supporting organizations are the CNR and the M.P.I.     

Reinvestigation of the quadrupole hyperfine structure in rotational spectra of 3-lodopropene

Quadrupole hyperfine structure of 3-iodopropene has been reinvestigated by the use of two methods, (1) Two-Level Approximation, and (2) Direct Solution of the Energy Matrix, to improve the discrepancies between the observed and calculated hyperfine spectra reported in a previous work (J. Mol. Spectrosc.66, 421–427 (1977)). Appreciable improvement can be found in the discrepancies between the observed and calculated spectra. By means of these two methods, the χ values of CH₂ICHCH₂ have been revised to be: |χ_ab| = 1160 MHz and χ_zz = ?1920 MHz, respectively.     

Born-Oppenheimer breakdown effects and hyperfine structure in the rotational spectra of SbF and SbCl

Pure rotational spectra have been measured for the ground electronic states of SbF and SbCl. The molecules were prepared by laser ablation of Sb metal in the presence of SF₆ or Cl₂, respectively. Their spectra were measured with a cavity pulsed jet Fourier transform microwave spectrometer. Although both molecules have two unpaired electrons, they are subject to Hund’s coupling case (c), and have X₁0⁺ ground states. The spectra have been interpreted with the formalism of ¹Σ⁺ molecules. For both molecules spectra of several isotopomers have been measured in the ground and first excited vibrational states. Large hyperfine splittings attributable to both nuclear quadrupole coupling and nuclear spin-rotation coupling have been observed. A Dunham-type analysis has produced unusually large Born-Oppenheimer breakdown parameters, which are interpreted in terms of the electronic structures of the molecules.     

Theory of the rotational structure of resonant Raman scattering by diatomic molecules

The apparatus of irreducible tensor operators is used to calculate the rotational structure of resonant Raman light scattering by freely rotating diatomic molecules. It is shown that solution of the problem reduces to the calculation of certain special coefficients. Their relation to the Placzek-Teller factors (which are well known in the theory of polarizability) is established. The nonzero coefficients are computed for the case when resonant rotational scattering is due to the¹ terms of the diatomic molecule.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 54–58, October, 1987.The author thanks T. N. Popov for interest in the work.     

Microwave spectrum and rotational isomerism of n-propyl isocyanide

The microwave spectrum of n-propyl isocyanide has revealed the existence of two rotational isomers, trans (methyl trans to the isocyanide substituent), and gauche. Plausible structures have been fitted to the data, giving the gauche dihedral angle as 119° ± 2° from the trans position. Stark effect measurements have yielded dipole moments for the two rotamers: μ_trans = 4.16 ± 0.02 D and μ_gauche = 4.10 ± 0.09 D. The rotational constants of the trans form are A = 23 700 ± 100, B = 2407.632 ± 0.020, and C = 2278.853 ± 0.030 MHz, and those of the gauche form are A = 10 208.983 ± 0.030, B = 3479.219 ± 0.015, and C = 2859.981 ± 0.015 MHz. It has been found from relative intensity measurements that the gauche ground state is slightly more stable than the trans ground state, with an energy difference of 99 ± 45 cm^?1. Several vibrationally excited states have been assigned to the torsional motion around the central carbon-carbon bond, the CNC bending motion, and the methyl internal rotation. The torsional vibration frequency is 114 ± 20 cm^?1 in the trans form and 123 ± 20 cm^?1 in the gauche form. A four-term potential function for internal rotation about the central CC bond has been determined.     

Microwave spectroscopy measurements of the hyperfine structure in antiprotonic 3He

We shall present here the first experimental results for microwave spectroscopy of the hyperfine structure of antiprotonic He-3 and a comparison to numerical simulations of the measurement. Due to the helium nuclear spin, antiprotonic He-3 has a more complex hyperfine structure than antiprotonic He-4 which has already been studied before. Thus a comparison between theoretical calculations and the experimental results will provide a more stringent test of the three-body quantum electrodynamics (QED) theory. The comparison of measured data to simulations allows to investigate the collisional processes between the helium atoms of the target medium and the antiprotonic helium atomcules. The collision rates can not be calculated exactly, but estimated by comparison of numeric simulations with the experimental results. Two out of four super-super-hyperfine (SSHF) transition lines of the (n, L)?=?(36, 34) state were observed. The measured frequencies of the individual transitions are 11.12559(14)?GHz and 11.15839(18)?GHz, less than 1?MHz higher than the current theoretical values, but still within their estimated errors. The frequency difference between the two lines also agrees with theoretical calculations.     

Microwave spectrum and structure of furfural

The microwave spectrum of furfural was investigated in the frequency range 7 GHz-21 GHz and 49 GHz-330 GHz. The ground and first torsional state of trans-furfural and ground state of cis-furfural were assigned and analyzed. A total of 1720 rotational lines with J up to 100 and K_a up to 53 were assigned to the ground state of trans-furfural, 1406 rotational lines with J up to 100 and K_a up to 48 were assigned to the first torsional state of trans-furfural and 2103 rotational lines with J up to 90 and K_a up to 48 to the ground state of cis-furfural. Accurate sets of centrifugal distortion constants for both conformations have been determined for the first time. The spectra of all ¹³C and ¹⁸O singly substituted isotopic species were observed in natural abundance in the 7 GHz-21 GHz range. Molecular structure co-ordinates, bond lengths and angles of the Kraitchman substitution type (r_s) and pseudo-Kraitchman type (r_pKr) are derived from the isotopic studies.     

The electronic spectrum of PrO. Energy linkages,rotational analysis,and hyperfine structure for systems XVII and XXI

Doppler-limited laser excitation spectra for four bands of PrO have been recorded: System XvII 0-0, System XXI 0-0 and 0–1, and the 0-0 intercombination between the upper and lower states, respectively, of Systems XVII and XXI. First lines in R and P branches prove that Systems XVII and XXI are, respectively, $\text{Ω}\text{′ = 4.5 ?}\text{Ω}\text{″ = 3.5}$ and $\text{Ω}\text{′ =}\text{Ω}\text{″ = 4.5}$. Hyperfine components are well resolved for all four excitation bands. Rotational and hyperfine constants are determined by least-squares fits of data from all four bands together. In addition, fluorescence spectra, recorded from various J′, v′ = 0 levels of the upper states of Systems XVII and XXI, reveal five new low-lying states. Principal constants (in cm^?1) for nine $\text{Ω-states}$ follow (1σ uncertainty in parentheses):

     

State	$\text{T}{}_{\mathrm{v}}$	$\text{B}{}_{\mathrm{v}}$	$\text{d}\text{(hfs)}$
$\text{Ω′ = 4.5 (System XXI)}$	18 882.388 (2)	0.353001 (18)	0.12403 (71)
$\text{Ω′ = 4.5 (System XVII)}$	16 594.075 (1)	0.353736 (20)	0.12977 (67)
$\text{Ω}\text{″ = 3.5}$	3 887.15 (16)	0.35751 (28)	—
$\text{Ω}\text{″ = 3.5}$	2 931.66 (15)	0.35712 (21)	—
$\text{Ω}\text{″ = 4.5}$	2 155.16 (30)	0.36264 (67)	—
$\text{Ω}\text{″ = 5.5}$	2 099.16 (31)	0.35079 (71)	—
$\text{Ω}\text{″ = 3.5}$	2 064.34 (13)	0.35654 (20)	—
$\text{Ω″ = 4.5 (System XXI)}$	217.383 (1)	0.362134 (20)	0.27744 (66)
$\text{Ω″ = 3.5 (System XVII)}$	0.0	0.360948 (16)	?0.00809 (85)