Spin-rotation Coupling Research Articles

Nuclear quadrupole hyperfine structure in the l-type spectra of chloro-, deuterochloro-, and bromoacetylene in the v5 = 1 1 vibrational states

The l-type doublets of the J = 2-1 rotational transitions of chloroacetylene, deuterochloroacetylene, and bromoacetylene in the v 5 = 1 1 states have been accurately remeasured and analyzed. Based on the results, direct l-type transitions in the frequency range 4–12 GHz have been assigned for the first time. All transitions showed halogen nuclear quadrupole hyperfine structure. For bromoacetylene, an asymmetry in the spin-rotation coupling of bromine has been detected.

The Microwave Spectrum of Isopropyl Iodide: The Iodine Hyperfine Structure and a Centrifugal Distortion Analysis

Abstract The ground stafe microwave spectrum of isopropyl iodide has been investigated by microwave Fourier transform (MWFT) spectroscopy. 212 hyperfine components of 39 mainly a-type transitions have been assigned from the measured spectra in the frequency range between 4 and 30 GHz. With a MWFT double resonance modulation (MWFTDR) spectrometer a weak c-type transition and a "forbidden" ΔJ = 2 line could be observed. The spectra were analysed using a diagonalization procedure of the complete Hamiltonian matrix and a simultaneous least squares fit of the rotational, quartic centrifugal distortion and the iodine quadrupole and spin rotation coupling constants directly to the measured frequencies. A set of 14 constants could be obtained with high accuracy. The rotational constant A and some of the centrifugal distortion constants could be improved using some large higher order quadrupole perturbations and the results of the MWFTDR measurements for the analysis.

The microwave fourier transform, millimeter-wave, and submillimeter-wave rotational spectra of isocyanogen, CNCN

The rotational spectra of isocyanogen, CNCN, and its four monosubstituted isotopomers 13CNCN, CN 13CN, C 15NCN, and CNC 15N in natural abundance in the ground vibrational state have been investigated in the spectral region from 10 to 550 GHz. The nuclear electric quadrupole hyperfine structures of the low- J transitions of the various isotopomers and of CNCN in three excited vibrational states have been analyzed and precise nuclear quadrupole coupling constants for the two 14N nuclei have been obtained. For 12C 14N 12C 14N the magnetic spin-rotation coupling constants could also be determined. The high- J millimeter- and submillimeter-wave transitions allowed the determination of accurate rotational and centrifugal distortion constants of all five isotopomers. From the respective moments of inertia a complete r s-structure for CNCN has been obtained: ▪ The permanent electric dipole moment of CNCN in its ground vibrational state was determined by Stark-effect measurements to be 0.7074(52) D.

The spin-rotation interactions in the methoxy radical

The spin-rotation coupling splitting in the à 2 A 1 state of CH3O has for the first time been spectrally resolved and measured using a very high resolution laser induced fluorescence apparatus. Both the spin-rotation parameters for the à state and the previously measured ones of the Xtilde; state are discussed in terms of first and second order contributions. A good understanding of all the measured constants is obtained, including the major Jahn-Teller induced contribution in the ground state.

Non-reactive interaction of oxirane and hydrogen bromide: isolation of an oxirane–hydrogen bromide dimer in a supersonic jet and its characterisation by microwave spectroscopy

The rotational spectra of the two isotopomers (CH2)2O⋯H79Br and (CH2)2O⋯H81Br of a dimer formed between oxirane and hydrogen bromide have been detected with a pulsed-nozzle, Fourier-transform microwave spectrometer. A fast-mixing nozzle was used to form and then isolate the observed species before the rapid ring-opening reaction could occur. Rotational constants, centrifugal distortion constants, and Br nuclear hyperfine (quadrupole and spin-rotation) coupling constants were determined. The following constants in particular were used to diagnose the nature of the observed species: [graphic omitted] A detailed analysis of the observed rotational constants allows the conclusion that the dimer has Cs symmetry with a pyramidal arrangement at oxygen and an oxirane geometry essentially unperturbed on dimer formation. When H of HBr is assumed to lie between O and Br the distance r(O⋯Br)= 3.2623 (12)A and the angle ϕ= 78.45 (9)° are determined. Diagonalization of the complete Br nuclear quadrupole coupling tensor leads to χzz=–202.457 MHz and χyy=–205.527 MHz, indicating that the presence of the oxirane molecule only slightly perturbs the cylindical symmetry of the HBr subunit. The angle of rotation of (αza)χ= 23.3° required to diagonalize the χ tensor is ca. 10° larger than the angle (αza)struct implied by the determined geometry. This suggests that the angle O⋯H—Br might be correspondingly less than 180°, i.e. the hydrogen bond might be slightly bent.

13C and 77Se spin-lattice relaxation in carbon diselenide at several magnetic fields. Determination of relative chemical-shift anisotropies and spin-rotation couplings

13C and 77Se spin-lattice relaxation in carbon diselenide at several magnetic fields. Determination of relative chemical-shift anisotropies and spin-rotation couplings

The Molecular Zeeman Effect of Imines. I. Methanimine, its Molecular g-Tensor, its Magnetic Susceptibility Anisotropies, its Molecular Electric Quadrupole Moment, its Electric Field Gradient at the Nitrogen Nucleus, and its Nitrogen Spin-Rotation Coupling

Abstract The rotational Zeeman effect has been observed in methanimine which was produced from ethylenediamine by flash pyrolysis. The observed vibronic ground state expectation values of the molecular g-values, the magnetic susceptibility anisotropies and the molecular electric quadrupole moments are: gaa = -1.27099(22), gbb= -0.18975(7), gcc= -0.03440(8), 2ξaa-ξbb-ξcc = 12.49(19) · 10-6 ergG-2mol-1, 2ξbb-ξcc-ξaa = 5.22(11) · 10-6 ergG-2 mol-1 Qaa = 0.43(17) · 10-26esu cm2, Qbb= 1.08(10) · 10-26 esu cm2, and Qcc= -1.51 (26) . 10-26 esu cm2. With the TZVP ab initio value for the out-off plane electronic second moment as additional input, reliable values can be given also for the individual components of the magnetic susceptibility tensor and for the bulk susceptibility: ξ = (ξaa + ξbb + ξcc)/3=-13.13(88) · 10-6 erg G -2 mol-1. From low-J a-and b-type zero field transitions the spin-rotation coupling constants and the 14N nuclear quadrupole coupling constants could be redetermined with improved accuracy. These data are compared with our new theoretical results.

Matrix isolation nuclear magnetic resonance studies of methyl group spin–rotation coupling

In dilute rare gas matrices containing acetonitrile or methyl acetylene, the methyl group rotates almost freely about a fixed symmetry axis in a large fraction of the matrix trapping sites. The secular spin–rotation interaction of the methyl protons does not vanish in this case, and we show this leads to resolved, temperature dependent splitting of the proton NMR lines. In addition, ordering of the methyl spins with respect to both spin–rotation and dipolar local magnetic fields occurs after a sudden change in the matrix temperature. This is shown to be consistent with the mechanism of the Haupt effect, a spin conversion process which restores rotational equilibrium after the temperature jump. Since the spin–rotation splitting provides a direct measure of the methyl group angular momentum, dynamical information pertaining to the matrix isolated molecule is obtained from the proton spectrum, providing a considerable simplification over spin relaxation measurements. Using a 0.5% CH3CN/Kr matrix as a prototypal system, the experimental observations are found to be consistent with the proposed form of the spin–rotation interaction. Several conclusions are reached regarding the hindering of methyl rotation by the solid rare gas lattice, dynamics in the trapping site, and the distribution of these sites in the matrix.

Molecular structure of iodoacetylene

The pure rotational spectra of iodoacetylene and its [1- 13C]-, [2- 13C]-, and [D]-isotopomers have been assigned. From the set of four rotational constants obtained, the r 0-structure and the partial r s-structure of the ethynyl moiety have been determined. From the hyperfine structures the nuclear quadrupole and spin-rotation coupling constants of iodine have also been measured.

Deuterium Quadrupole Coupling Constants in Deuterochloroacetylene

Abstract The deuterium and chlorine nuclear quadrupole coupling constants have been determined for both of the chlorine isotopomers of deuterochloroacetylene (DCCC1), along with the rotational, centrifugal distortion, and chlorine spin-rotation coupling constants. The values are B = 5186.97631 (22) MHz, DJ= 1.13(2) kHz, eQq(Cl)= -79.7358(19) MHz, cI(Cl) = 1.10(31)kHz, and eQq(D) = 207.0(28)kHz for DCCCl-35, and B = 5084.17839(30) MHz, DJ = 0.99(2) kHz, eQq(Cl)= -62.8451(27) MHz, cI(CI) = 0.76(43) kHz, and eQq(D) = 205.8(39)kHz for DCCCl-37.

The microwave spectrum of the CP radical and related astronomical search

view Abstract Citations (33) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Microwave Spectrum of the CP Radical and Related Astronomical Search Saito, Shuji ; Yamamoto, Satoshi ; Kawaguchi, Kentarou ; Ohishi, Masatoshi ; Suzuki, Hiroko ; Ishikawa, Shin-Ichi ; Kaifu, Norio Abstract The rotational spectrum of the CP radical was detected in the laboratory by using a source-modulated microwave spectrometer combined with a free space absorption cell. The CP radical was produced by a dc-glow discharge in a mixture of PH3, CH4, and He. Nineteen lines of five rotational transitions were observed in the frequency region of 95-334 GHz and were least-squares analyzed to determine the molecular constants: the rotational constant, the centrifugal distortion constant, the spin-rotation coupling constant, and hyperfine coupling constants for the phosphorus nucleus. Based on the measured and calculated line frequencies, astronomical searches for the interstellar CP radical were made in Orion-KL, Sgr B2, W51A, TMC-1, and IRC + 10216, for which upper limits to the column density were estimated. Publication: The Astrophysical Journal Pub Date: June 1989 DOI: 10.1086/167570 Bibcode: 1989ApJ...341.1114S Keywords: Free Radicals; Interstellar Matter; Microwave Spectra; Molecular Rotation; Carbon; Line Spectra; Phosphorus; Spectrum Analysis; Astrophysics; INTERSTELLAR: MOLECULES; LABORATORY SPECTRA; LINE IDENTIFICATIONS; MOLECULAR PROCESSES full text sources ADS | data products SIMBAD (6)

Stern–Gerlach deflection spectra of nitrogen oxide radicals

Magnetic deflection spectra of beams of pure NO2 and NO2 seeded into rare gases have been determined using a Stern–Gerlach apparatus. Using He as carrier, a simple two-line deflection pattern is observed, indicating the breakdown of spin–rotation coupling in fields of 10 kG or more. Use of the other rare gases as carriers yields the two satellites at positions dictated by the beam velocities, and in addition, a more-or-less intense component at zero deflection which we hold to be due to diamagnetic or weakly paramagnetic (NO2)x clusters. The deflection amplitudes and line shapes are in good agreement with calculations. Additional weak bands observed in the spectra are likely due to van der Waals clusters such as NO2 ⋅ Ar and NO2 ⋅ Ne. 14N/15N isotope effects in NO2 were visible as changes of line shape. Zeeman level anticrossings are calculated quantum mechanically to occur for NO2 in the 20–30 kG regime, however their effects are small and were not observed. Deflection spectra of NO in its 2Π3/2 thermally excited state were obtained showing satellites at the positions predicted assuming pure Hund’s case-a coupling. Modeling of the observed spectra shows that both the electronic and rotational temperatures of the NO in the beam are rather high (20–125 K). The observed magnetic deflection spectra of the dialkyl nitroxide TEMPO when combined with line-profile calculations do not support the suggestion of Amirav and Navon [Chem. Phys. 82, 253 (1983)] that this molecule undergoes significant intramolecular spin relaxation while in the magnetic gap. In contrast, the SG spectra of the related radical di-t-butyl nitroxide shows no magnetic deflection, suggesting a spin lifetime of 0.5 μs or less.

The Iodine Hvperfine Structure in the Microwave Spectrum of Ethyl Iodide: Nuclear Quadrupole and Spin Rotation Coupling

Abstract Some rotational transitions of ethyl iodide, CH3CH2I, have been reinvestigated by microwave Fourier transform (MWFT) spectroscopy. The iodine hyperfine structure splittings were first ana lyzed using a direct diagonalization procedure of the complete quadrupole Hamiltonian matrix. The results of this analysis showed deviations from our measurements up to 60 kHz. A new analysis using additional spin rotation coupling matrix elements reproduces our measurements within the experi­mental error limit and decreases the standard deviation of the least squares fit from 28 kHz to only 4 kHz.

Laboratory detection of a new interstellar free radical CH2CN(2B1).

An asymmetric-top free radical CH2CN, which as a 2B1 ground state, was detected for the first time by laboratory microwave spectroscopy. The radical was produced in a free-space absorption cell by a DC glow discharge in pure CH3CN gas. About 60 fine-structure components were observed for the N = 11-10 to 14-13 a-type rotational transitions in the frequency region of 220-260 GHz, and many hyperfine resolved components for the N = 4-3 and 5-4 transitions in the 80 and 100 GHz regions, respectively. The molecular constants, including the rotational constants, centrifugal distortion constants, and spin-rotation coupling constants with centrifugal distortion correction terms were determined from the fine-structure resolved transitions, and the hyperfine coupling constants due to the hydrogen and nitrogen nuclei were obtained from the low-N transitions. As a result we assigned U100602 and U80484 from Sgr B2, and U40240 and U20120 from TMC-1, to the N = 5-4, 4-3, 2-1, and 1-0 transitions with K-1 = 0 of the CH2CN radical.

Deuterium Quadrupole Coupling Constants of Deuterohalogenoacetylens

Abstract Employing the high resolution of microwave Fourier transform spectroscopy, we investigated the lowest rotational transitions of fluoro-, bromo-, and iodoacetylene-d. Along with the rotational, centrifugal distortion, halogen nuclear quadrupole, and halogen spin-rotation coupling constants, we determined the deuterium quadrupole coupling constants of bromo-and iodoacetylene-d. For fluoroacetylene-d, we redetermined the deuterium nuclear quadrupole coupling constants with higher accuracy.

The microwave spectrum of cyanogen iodide: Hyperfine structure by coupling of two nuclei and centrifugal distortion analysis

The first four rotational transitions of cyanogen iodide (ICN) have been investigated by microwave Fourier transform (MWFT) spectroscopy to determine the quadrupole and spin-rotation coupling parameters of iodine and nitrogen. The millimeter-wave and submillimeter-wave spectra have also been measured from 45 GHz ( J = 6) up to 758 GHz ( J = 117). Thse data have been used to determine accurately the rotational constant, the quartic and sextic centrifugal distortion constants, and the hyperfine centrifugal distortion constant χ J(I) which is a measure of the change of eqQ(I) by centrifugal distortion.

Relaxation of gaseous spin-polarized 3He targets due to ionizing radiation.

The theory of spin-polarized $^{3}\mathrm{He}$ relaxation due to hyperfine coupling in $^{3}\mathrm{He}^{+}$ and due to spin-rotation coupling in $^{3}\mathrm{He}_{2}^{+}$ is presented. Comparison is made between the theory and recent experiments which utilized spin-polarized $^{3}\mathrm{He}$ as a charged-particle beam target. The theory predicts that at low He pressures applying a magnetic field significantly reduces the $^{3}\mathrm{He}$ depolarization rate due to formation of $^{3}\mathrm{He}_{2}^{+}$. At high He pressures the relaxation rate decreases with pressure. In addition, charge-transfer processes with foreign gases suppress $^{3}\mathrm{He}$ depolarization by reducing the $^{3}\mathrm{He}^{+}$ and $^{3}\mathrm{He}_{2}^{+}$ concentrations.

The analytic representation of radial functions determined from the spectra of diatomic molecules

An alternative approach to the derivation of the expressions for the function Z kl (to take account of effects beyond the vibrational and rotational motions of the nuclei) in the term coefficients of diatomic molecules is outlined. Application of the resulting expressions is made to the spinrotational coupling parameter of 12C 14N in the X 2Σ state and to the electric quadrupolar coupling parameter of the 35C l nucleus in H 35C l.

The Microwave Spectrum of Cyanogen Iodide-15N: Hyperfine Structure and Electric Dipole Moment Investigated by Microwave Fourier Transform Spectroscopy

The first rotational transition of cyanogen iodide-15N (IC15N) has been investigated by microwave Fourier transform (MWFT) Stark effect spectroscopy to determine the electric dipole moment. In addition the first four rotational transitions have been measured by MWFT spectroscopy to obtain accurate parameters for the rotational, quadrupole and spin-rotation coupling parameters.

Determination of Quadrupole and Spin-Rotation Coupling in the Rotational Spectrum of Carbonylsulfide-33S and -17O

The quadrupole and spin rotation coupling constants are determined by analysis of the J = 0 - 1 and J = 1 - 2 transitions o f OC33S and 17OCS in natural abundance. The data are compared with those obtained from molecular beam electric resonance and very recent pulsed beam microwave Fourier transform spectroscopy.