Nuclear Spin-rotation Constants Research Articles

The pure rotational spectrum of yttrium monobromide

The pure rotational spectrum of the X 1Σ+ ground electronic state of yttrium monobromide has been measured. This is the first high-resolution spectrum recorded for this molecule. Transitions in the ground and first excited vibrational states have been measured for both the Y79Br and Y81Br isotopomers. Equilibrium rotational parameters have been determined and an equilibrium bond distance has been calculated. Vibrational parameters have been estimated. Hyperfine structure due to the bromine nuclei has been observed and nuclear quadrupole and nuclear spin–rotation constants have been determined. These parameters have been used to investigate the ionic character of the Y–Br bond and comparisons have been made to several alkali and alkaline earth metal bromide species.

Laboratory Rotational Spectrum of PH (N = 2 ← 1) in the 1 THz Region

Abstract The N = 2 ← 1 rotational transition of the PH radical in its ground electronic (X3 Σ- ) and vibrational states has been measured with the Cologne terahertz spectrometer in the frequency region between 920 and 1070 GHz. The PH radical was generated by immersing red phosphorus in a dc glow discharge of molecular hydrogen buffered with argon. Transition frequencies of the five J′ - J″ fine structure components together with the associated hyperfine structure patterns were precisely measured and analyzed to derive highly accurate molecular parameters, which are more extensive than those reported in the existing literature. Among the determined parameters are the rotational constant B0 = 252200.8099(63) MHz and the centrifugal distortion constant D0 = 13.2915(33) MHz, as well as two fine structure constants - the spin-rotation constant γ0 and the spin-spin interaction constant λ0 - together with their centrifugal distortion contributions Dγ0 and Dλ0. Furthermore, each of the magnetic hyperfine parameters bF, c, and the nuclear spin-rotation constants CI were obtained for both nuclei. The accuracy of previously obtained molecular constants has been improved by up to one order of magnitude. This new set of molecular parameters allows highly reliable frequency predictions of the rotational spectrum extending into the far infrared region; such transition frequencies may be of interest for interstellar spectroscopy.

MCSCF nuclear magnetic shieldings and spin-rotation constants of [formula omitted]O in [formula omitted]O [formula omitted]O [formula omitted]O and [formula omitted]O [formula omitted]O [formula omitted

The nuclear magnetic shieldings of ozone and the 17 O nuclear spin-rotation constants for the two isotopomers 16 O 17 O 16 O and 17 O 16 O 16 O have been calculated using the multiconfigurational self-consistent field response approach. A large basis set together with a restricted active space wavefunction involving more than thirteen million determinants in the largest calculation have been used. Origin dependencies were eliminated by using London atomic orbitals for the chemical shieldings and rotational London atomic orbitals for the spin-rotation constants. We compare our results for the shieldings both with experiment and other accurate theoretical results. For the 17 O nuclear spin-rotation constants of the two isotopomers of ozone we present fully ab initio estimates, which we compare to recent experimentally determined values.

Isotope and temperature effects on nuclear magnetic shieldings and spin-rotation constants calculated at the coupled-cluster level

The temperature dependence of nuclear shieldings as well as isotope effects on shieldings and spin-rotation constants have been computationally investigated for H2, HF, F2, CO, and N2 employing the coupled-cluster singles and doubles (CCSD) method augmented by a perturbative treatment of triple excitations (CCSD(T)) for the calculation of potential curves, shieldings and spin–rotation functions together with finite-element techniques for the solution of the rovibrational problem. Calculated and measured temperature dependence of the isotropic shieldings agrees for N2, while for CO and F2 the computed temperature dependence is smaller than the experimental result. Isotropic shieldings have been deduced on the basis of our calculations from the measured spin-rotation constants for four isotopomers of H2 and agree, as required by theory. However, calculated and measured temperature dependence of the isotope shifts between HD and D2 differ by up to 10% which is larger than the estimated error bars for the exp...

Isotope and temperature effects on nuclear magnetic shieldings and spin-rotation constants calculated at the coupled-cluster level

The temperature dependence of nuclear shieldings as well as isotope effects on shieldings and spin-rotation constants have been computationally investigated for H2, HF, F2, CO, and N2 employing the coupled-cluster singles and doubles (CCSD) method augmented by a perturbative treatment of triple excitations (CCSD(T)) for the calculation of potential curves, shieldings and spin–rotation functions together with finite-element techniques for the solution of the rovibrational problem. Calculated and measured temperature dependence of the isotropic shieldings agrees for N2, while for CO and F2 the computed temperature dependence is smaller than the experimental result. Isotropic shieldings have been deduced on the basis of our calculations from the measured spin-rotation constants for four isotopomers of H2 and agree, as required by theory. However, calculated and measured temperature dependence of the isotope shifts between HD and D2 differ by up to 10% which is larger than the estimated error bars for the experimental values. For HF and CO, calculated and measured isotope shifts agree, while for N2 no experimental data for comparison are available. In case of spin–rotation constants, the calculated dependence on the rotational angular momentum quantum number are for both H2 and F2 in good agreement with the dependence deduced from measurements, while for HF not enough experimental data are available for a comparison.

Nuclear hyperfine interactions in the microwave spectrum of aluminium isocyanide

The pure rotational spectrum of AINC has been measured between 11.9 and 24.0 GHz using a pulsed jet Fourier transform microwave spectrometer. The molecule was produced using a laser ablation source, in which the ablated Al metal reacted with cyanogen present in the Ar backing gas of the jet. Hyperfine structure due to both the 27Al and 14N nuclei has been observed. Nuclear quadrupole coupling constants and nuclear spin-rotation constants have been determined for both nuclei along with an Al N nuclear spin-spin coupling constant. The electronic structure of AINC has been investigated by estimating the degree of sp-hybridisation of the Al and N bonding orbitals. Comparisons have been made to similar linear metal isocyanide and aluminium halide species.

The microwave spectrum of the NH2 radical: The hyperfine structure of the 2B1 ground electronic state

The pure rotational spectrum of the NH2 radical in its X̃ 2B1 ground electronic state was measured in the frequency region of 230–470 GHz by microwave spectroscopy. The radical was generated in a free space cell by dc-glow discharge of NH3. Seventy nine fine and hyperfine components of four rotational transitions were measured, and were analyzed by least squares methods. The hyperfine coupling constants for both the nitrogen and hydrogen nuclei were redetermined with higher precision than those of the previous analysis for microwave optical double resonance (MODR) data. The nuclear spin–rotation constants for the hydrogen nucleus as well as the nitrogen nucleus were found to be anomalously large. The anomalous constant of Caa(H) is interpreted by the same reason for the anomalous large value for Caa(N) originating from the large A constant and the relatively low-lying à 2A1 electronic state.

Fourier-transform microwave spectroscopy of InF, InCl, and InBr, prepared using laser ablation

High-resolution rotational spectra of InF, InCl, and InBr have been measured with a pulsed jet cavity Fourier-transform microwave spectrometer. Samples were prepared by vaporizing In with a pulsed Nd:YAG laser, and reacting the vapour with a precursor gas entrained in the Ne backing gas of the jet. Precise rotational and nuclear quadrupole coupling constants have been obtained for all these molecules, along with the first nuclear spin–rotation constants of InCl and InBr. The hyperfine coupling constants are discussed in terms of the electronic structures of the molecules.

The nuclear magnetic shielding and spin-rotation constants of the hydrogen molecule

The variation-perturbation method, employing an explicitly correlated basis set in the form of Gaussian functions with exponential correlation factors, has been used to calculate the paramagnetic component of the nuclear magnetic shielding and the electronic contribution to the spin-rotation constant for the hydrogen molecule in its ground state. The diamagnetic components of the shielding tensor have also been computed. The computations have been performed for three internuclear distances in the vicinity of equilibrium. A comparison of the calculated quantities, which are of high accuracy, with the experimental data reveals a small but significant discrepancy between theory and experiment.

Rotational Spectra of 14N17O and 15N18O

Abstract The mm-wave spectra of 15N18 O and 14N 17 O in both X2 Π1/2 and X2 Π3/2 states have been measured and assigned for the first time. Improved rotational and, for the first time, 17O hyperfine coupling constants have been derived from the analysis. The 14N17 O data yield parameters of the unpaired electron spatial distribution near both nuclei. Furthermore, the deviation from the Born-Oppenheimer approximation is confirmed on the basis of the rotational constants of five isotopomers. Finally, when comparing the nuclear spin-rotation constants to the ones of other molecules containing 14N or 17O nuclei, a roughly linear proportionality with the rotational constant B is found.

Hyperfine structure of theR(115) 20-1 line of127I2 at 570 nm

The hyperfine spectrum of the iodineR(115)20-1 line, at 570 nm, was obtained by conventional saturated absorption spectroscopy. The differences of nuclear electric-quadrupole (Δe Qq) and spin-rotation (ΔC) constants between theB andX states were determined by a least-square fit to the experimental data. This line may provide a good frequency reference in coincidence with the1S0-1P1 resonant transition of magnesium, at 285 nm, when this one is investigated with frequency doubled lasers.

The Hyperfine Structures of CuCl and CuBr in Their Ground States Studied by Microwave Fourier Transform Spectroscopy

The hyperfine structure of the J = 1 ← 0 rotational transition of CuCl as well as the J = 3 ← 2, 2 ← 1, and 1 ← 0 rotational transitions of CuBr in the v = 0 vibrational level have been investigated using a microwave Fourier transform spectrometer. The molecules were produced by laser ablation of the copper halide followed by an axial supersonic expansion into a near-semiconfocal Fabry-Perot cavity. The analysis of the hyperfine structure yielded improved values of the rotational and electric quadrupole constants and determined the nuclear spin-rotation constants for the first time. The physical implications of these results are discussed.

Nuclear Quadrupole Coupling, Spin-Rotation, and Spin-Spin Interaction in the Rotational Spectrum of Ethinylisocyanide

The rotational J = 1-0 transitions of nine different isotopomers of ethinylisocyanide, H-CC-NC, were measured with high resolution using a pulsed molecular beam microwave Fourier transform (MB-MWFT) spectrometer. The analysis of the complex hyperfine patterns yielded nuclear quadrupole, spin-rotation, and spin-spin interaction constants.

Hyperfine structure of Na2.

The hyperfine structure has been measured in several rotational states of the X${}^{1}$${\ensuremath{\Sigma}}_{g}^{+}$, v''=0 ground state of ${\mathrm{Na}}_{2}$ with the aid of the laser-rf double-resonance technique on a molecular beam. The rotational states observed were especially chosen to avoid distortion of the line shapes by laser-induced coherence effects. The electric quadrupole, nuclear spin-rotation, tensor spin-spin, and scalar spin-spin hyperfine coupling constants are, respectively, eqQ=[-458.98(4)-0.007 28(25)J(J+1)] kHz, c=242.9(1.5) Hz, d=302.6(5.0) Hz, and \ensuremath{\delta}=1066.7(6.5) Hz.

An approximate absolute 33S nuclear magnetic shielding scale

Sulfur-33 chemical shifts have been measured for a number of simple compounds, e.g. SF6, HFSO3, X2SO2, SO2, Cl2SO, CH3SH, H2S, and OCS, which have not been previously reported. Our results indicate that the range of 33S chemical shifts is approximately 1000 ppm, slightly less than that observed for 17O and approximately one half the range reported for 77Se. Using the 33S nuclear spin-rotation constant of OCS measured by molecular-beam electric resonance and Flygare's procedure, an absolute 33S shielding constant of 843 ± 12 ppm is calculated for OCS, permitting an approximate absolute shielding scale to be proposed for this nucleus.

Molecular beam electric resonance spectroscopy of the nitric oxide dimer

Microwave and radiofrequency spectra have been observed for (NO)2 using the technique of molecular beam electric resonance spectroscopy. Precise values have been determined for rotational, nuclear quadrupole coupling and spin-rotation constants of the ground electronic state treated as a singlet state. The values obtained are A = 25829·4803(20) MHz, B = 5614·3093(4) MHz, C = 4605·4396(12) MHz xaa = -4·0652(2) MHz, xbb - xcc = -8·5498(6) MHz caa = 10·4(5) kHz, cbb = 13·8(4) kHz, ccc = 0·8(4) kHz. The electric dipole moment has also been determined: μ = 0·17120(2) D. From these data (NO)2 is interpreted to have a symmetric cis-planar structure with the structural parameters r NN = 2·33(12) A, r NO = 1·15(1) A, ∠NNO = 95(5), 1/2(r NN + r NO) = 2·444(8) A. The quadrupole coupling constants of the nitrogen nuclei and the dipole moment demonstrate that little electron rearrangement occurs on dimer formation. In addition xaa and xbb - xcc indicate that the unpaired π electrons lie in the plane of the dimer imply...

The rotational spectrum and molecular parameters of BrO in the [formula omitted] state

The ν = 0 and 1 rotational spectrum of BrO in the 2 Π 3 2 state has been observed in selected regions between 60 and 400 GHz. The precision of previously measured parameters and the quality of the fit has been improved. In addition, the centrifugal distortion constant, D 02, the effective Λ-doubling constant, q eff, the perpendicular quadrupole coupling constant, eqQ 2, and a linear combination of the magnetic hyperfine constant, b, and nuclear spin-rotation constant, C rs, have been measured for the first time. The values of ω e and ω e x e derived from the mechanical constants are in good agreement with very recent optical data.

ChemInform Abstract: A PRECISE STUDY OF THE ROTATIONAL SPECTRUM OF FORMALDEHYDE H212C17O AND H213C17O

Abstract The pure rotational spectra of H 2 12 C 17 O and H 2 13 C 17 O have been investigated in the frequency region between 8 and 360 GHz in the ground vibrational state. For both isotopic species the 17 O nuclear quadrupole coupling constants and spin-rotation constants have been obtained. From both Q - and R -branch transitions a set of rotational constants and several distortion constants could be derived employing Watson's formalism in A reduction. The obtained rotational constants are in Megahertz: H 2 12 C 17 O H 2 13 C 17 O A 281 965.0 (30) 281 987.3 (19) B 37 812.287(45) 36 776.790(25) C 33 214.523(31) 32 412.920(19) This study reports the first measurement of the H 2 13 C 17 O rotational spectrum.

A precise study of the rotational spectrum of formaldehyde H 212C 17O and H 213C 17O

The pure rotational spectra of H 2 12C 17O and H 2 13C 17O have been investigated in the frequency region between 8 and 360 GHz in the ground vibrational state. For both isotopic species the 17O nuclear quadrupole coupling constants and spin-rotation constants have been obtained. From both Q- and R-branch transitions a set of rotational constants and several distortion constants could be derived employing Watson's formalism in A reduction. The obtained rotational constants are in Megahertz: H 2 12C 17O H 2 13C 17O A 281 965.0 (30) 281 987.3 (19) B 37 812.287(45) 36 776.790(25) C 33 214.523(31) 32 412.920(19) This study reports the first measurement of the H 2 13C 17O rotational spectrum.

Dipole Moment of ICI

The J = 2 ← 1 microwave spectra of I35Cl and I37Cl are measured for the v=0 and v=1 vibrational levels. The dipole moment μ (v = 0) = 1.24 ± 0.02 D is determined by Stark effect measurements. Improved values of the rotational and quadrupole coupling constants are obtained and the iodine nuclear spin—rotation constant is determined.