Electric Quadrupole Coupling Constants Research Articles

The Detection of Lines in the Microwave Spectrum of Indium Hydroxide, InOH, and Its Isotopomers

The rotational transition 101–000for InOH in its ground1A′ state has been detected with a pulsed microwave spectrometer; the molecule was generated by laser ablation of indium(III) hydroxide, In(OH)3. The same transition has also been recorded for two of its isotopomers, In18OH and InOD. Hyperfine structure arising from both the115In and1H (or2D) nuclei was observed. The results have been combined with others from UV spectroscopy to determine anr0structure for the molecule:r0(In–O) = 0.20167(4) nm,r0(O–H) = 0.0911(4) nm,∠InOH = 132.0(3)°.These values reflect the very marked effect of averaging over a large-amplitude bending vibration in InOH in its zero point level. Values for the115In and2D electric quadrupole coupling constants and for some smaller, magnetic hyperfine terms are also derived.

Laboratory Measurement of the [ITAL]J[/ITAL] = 1–0 Transition of AlH near 387 GHz

The J = 1-0 transition of AlH was measured in the 387 GHz frequency region with a submillimeter-wave spectrometer combined with a heat-pipe cell made of alumina. The AlH molecule was generated by a DC-glow discharge in a mixture of aluminum vapor and H2. The observed rotational transitions showed hyperfine structure, due to the aluminum nucleus, and their frequencies were precisely measured for astronomical use. The rotational constant and electric quadrupole coupling constant were precisely determined.

Isotope shifts and hyperfine structure of optical transitions in 147-150,152,154Sm II by fast-ion-beam-laser spectroscopy.

In this paper isotope shifts (IS's) and hyperfine structure hfs in 16 transitions of singly ionized samarium are presented. The IS's, which, to our knowledge, have not been determined previously, and the hfs are measured by collinear fast-ion-beam--laser spectroscopy. The ions are excited from metastable levels in the 4${\mathit{f}}^{6}$${(}^{7}$F)5d configuration to levels in the 4${\mathit{f}}^{5}$ 5d6s? and 4${\mathit{f}}^{6}$${(}^{7}$F)6p? configurations with laser light in the red and orange part of the visible spectrum. The IS's between the isotopes $^{147\mathrm{\ensuremath{-}}150,152,154}\mathrm{Sm}$ ii are measured for two transitions while the IS's between the even isotopes $^{148,150,152,154}\mathrm{Sm}$ ii are measured for the other 14 transitions. Three of the 14 transitions are not tabulated in the literature. Tentative compositions of the upper levels are evaluated from the IS's by using the sharing rule. The IS's measurements are also used in an absolute calibration of the acceleration voltage within an accuracy of 0.1%. The hfs of 10 levels are recorded. Corresponding magnetic-dipole and electric-quadrupole coupling constants, A and B factors, are evaluated. The A and B factors have not been determined before for three of the levels, and for the other levels they are determined with improved accuracy.

An ab initio study of the HNCN radical

The equilibrium structure for the ground state of the HNCN radical is calculated at the levels of the self-consistent field theory (SCF), the second-order Mo/ller–Plesset perturbation approximation (MP2), and the full single and double excitation coupled cluster theory including all connected triples in a noniterative manner [CCSD(T)], using various extended basis sets starting from 6–311 G(d,p). At the CCSD(T) level, the outer C–N bond is more than 0.1 Å shorter than the inner one and the N–C–N group departs from linearity by 6°. The total N–C–N length is in good agreement with the experimental value [Herzberg and Warsop, Can. J. Phys. 41, 286 (1963)], however, the H–N–C angle is about 6° smaller. The N–H bond is very close to a normal N–H bond but is about 0.2 Å smaller than the experimental estimate. Except for the smaller H–N–C angle, the geometrical parameters for HNCN closely parallel those for the triplet HCCN molecule. The dipole moment, harmonic frequencies, electric quadrupole, and Fermi contact coupling constants of HNCN are also calculated. The calculated harmonic frequencies confirm the preliminary assignments of Wu, Hall, and Sears [J. Chem. Soc. Faraday Trans. 89, 615 (1993)]. The quadrupole coupling constants for the inner and outer N atoms are comparable, implying a complex pattern of hyperfine split components in the lowest rotational transitions. The present calculation may thus serve as a useful guide for the interpretation of the rotational spectrum.

Lamb shifts and hyperfine structure in 6Li+ and 7Li+: Theory and experiment.

High-precision laser-resonance measurements accurate to \ifmmode\pm\else\textpm\fi{}0.5 MHz or better are reported for transitions among the 1s2s $^{3}$${\mathit{S}}_{1--}$1s2p $^{3}$${\mathit{P}}_{\mathit{J}}$ hyperfine manifolds for each of J=0, 1, and 2 in both $^{6}\mathrm{Li}^{+}$ and $^{7}\mathrm{Li}^{+}$. A detailed analysis of hyperfine structure is performed for both the S and P states, using newly calculated values for the magnetic dipole and electric quadrupole coupling constants, and the hyperfine shifts subtracted from the measurements. The resulting transition frequencies are then analyzed on three different levels. First, the isotope shifts in the fine-structure splittings are calculated from the relativistic reduced mass and recoil terms in the Breit interaction, and compared with experiment at the \ifmmode\pm\else\textpm\fi{}0.5-MHz level of accuracy. This comparison is particularly significant because J-independent theoretical uncertainties reduce through cancellation to the \ifmmode\pm\else\textpm\fi{}0.01-MHz level. Second, the isotope shifts in the full transition frequencies are used to deduce the difference in rms nuclear radii.The result is ${\mathit{R}}_{\mathrm{rms}}$${(}^{6}$Li)-${\mathit{R}}_{\mathrm{rms}}$${(}^{7}$Li)=0.15\ifmmode\pm\else\textpm\fi{}0.01 fm, in agreement with nuclear scattering data, but with substantially improved accuracy. Third, high-precision calculations of the low-order non-QED contributions to the transition frequencies are subtracted from the measurements to obtain the residual QED shifts. The isotope-averaged and spin-averaged effective shift for $^{7}\mathrm{Li}^{+}$ is 37 429.40\ifmmode\pm\else\textpm\fi{}0.39 MHz, with an additional uncertainty of \ifmmode\pm\else\textpm\fi{}1.5 MHz due to finite nuclear size corrections. The accuracy of 11 parts per million is the best two-electron Lamb shift measurement in the literature, and is comparable to the accuracies achieved in hydrogen. Theoretical contributions to the two-electron Lamb shift are discussed, including terms of order (\ensuremath{\alpha}Z${)}^{4}$ recently obtained by Chen, Cheng, and Johnson [Phys. Rev. A 47, 3692 (1993)], and the results used to extract a QED shift for the 2 $^{3}$${\mathit{S}}_{1}$ state. The result of 30 254\ifmmode\pm\else\textpm\fi{}12 MHz is shown to be in good accord with theory (30 250\ifmmode\pm\else\textpm\fi{}30 MHz) when two-electron corrections to the Bethe logarithm are taken into account by a 1/Z expansion method.

Quadrupole moment of the 7+ isomeric state in112In

The electric quadrupole coupling constant of the 7+ 350.8 keV isomeric state in112In has been measured by the TDPAD method in the polycrystalline metallic Cd lattice at 489 K. The determined quadrupole moment |Q| (7+)=103(3) fm2 was compared with the empirical estimation according to the additivity relation and the calculated value within the interacting boson-fermion-fermion/odd-odd truncated quadrupole phonon model. The quadrupole moment of the 8− 613.7 keV isomeric state has been remeasured as |Q|(8−)=9.5(3) fm2.

The millimeter-wave spectrum of AlOH

The pure rotational spectrum of the AlOH and AlOD molecules in their X 1Sigma(+) (v = 0) ground electric states has been measured in the laboratory using direct absorption millimeter/submillimeter spectroscopy. The species were produced by the reaction of aluminum vapor, created in a Broida-type oven, with hydrogen peroxide or D2O2. Eight rotational transitions of AlOH and five transitions for AlOD were measured in the frequency range of 157-378 GHz to an accuracy better than +/- 75 kHz. Electric quadrupole interactions, arising from the aluminum nuclear spin of 5/2, were observed in the J = 4 - 5 and the J = 5 - 6 transitions of AlOH. The rotational constants of these molecules have been determined from a nonlinear least-squares fit to the data. The electric quadrupole coupling constant, eqQ, has been measured as well, and was found to have a value of -42.4 +/- 4.3 MHz. The spectra are consistent with quasi-linear ground states for AlOH and AlOD, as predicted by theory. AlOH is of astrophysical interest because of the relatively high cosmic abundance of aluminum.

121-Sb Mössbauer study of insulating and ion-conducting antimony chalcogenide-based glasses

The local environment of antimony in As 2S 3Sb 2S 3, AgISb 2S 3, AsSbSe and A AgAsSbSe glasses, glassy/crystalline alloys and crystals is investigated using 121-Sb Mössbauer spectroscopy. The isomer shift both for sulfide and selenide vitreous alloys is 1.2–2.0 mm/s more positive than that for corresponding crystalline parents. The smaller s-electron density at the 121Sb nucleus for glasses indicates a decrease of the antimony-chalcogen interatomic distances in comparison with those for crystalline materials. The isomer shift systematics and composition dependencies of the electric-quadrupole coupling constant, eQV zz , and the asymmetry parameter, ν, shows that in As 2S 3Sb 2S 3 and AsSbSe insulating glasses an isomorphous substitution of arsenic by antimony occurs accompanied by an increase of interatomic distances. In the case of Ag + ion-conducting vitreous alloys, however, the antimony-chalcogen distances are governed by the silver content and do not depend on the Sb fraction of the glass. Geometric and topological disorder in the glass network is correlated with an increase of the electric-quadrupole coupling constants and values of the asymmetry parameter ν between 0.4 and 1.0.

Observation of55Mn NMR and NQR Signals from Site II in β Mn Metal

NMR and NQR signals of 55 Mn in site II were observed. The electric quadrupole coupling constant and the asymmetry parameter were estimated to be e 2 q Q / h =30 MHz and η∼0, respectively. The nuclear spin lattice relaxation rate, 1/ T 1 , is proportional to \(\sqrt {T}\), which indicates β Mn to be an itinerant antiferromagnetic system with T N ∼0 K. The value of 1/ T 1 at site II is about 20 times larger than the value at site I. The electronic state of Mn at site II is more magnetic than that at site I.

Hyperfine-structure studies of ^93Nb by laser optogalvanic spectroscopy

The hyperfine structure of 22 states of niobium is studied by Doppler-limited laser optogalvanic spectroscopy. The sample was prepared by a sputtering technique employing a niobium–neon hollow-cathode lamp. A frequency-stabilized single-frequency ring dye laser was used for excitation, and optogalvanic spectroscopy techniques were used for detection. From the recorded well-resolved hyperfine spectra the magnetic dipole and electric quadrupole coupling constants are evaluated. The hyperfine coupling constants for 13 states belonging to the configurations 4d45s, 4d45p, and 4d35s5p are being reported for the first time to our knowledge. The values obtained are compared with previous data when available.

2 D Methods in NQR Spectroscopy

Abstract The application of two-dimensional spectroscopy to nuclear quadrupole resonance (NQR) is reviewed with special emphasys on spin 3/2 nuclei. A new two-dimensional level crossing double resonance NQR nutation technique based on magnetic field cycling is described. This technique allows for a determination of both the electric quadrupole coupling constant and the asymmetry parameter for spin 3/2 nuclei in powdered samples even in cases where the quadrupolar signals are too weak to be observed directly. It works if the usual double resonance conditions are met, i.e. if the spin-lattice relaxation times are not too short if the quadrupolar nuclei are dipolarly coupled to "strong" nuclei. Variations of this techique can be also used for 2 D "exchange" NQR spectroscopy and NQR imaging.

Rotational spectra, structure, and intramolecular force field of the Hg–OCS van der Waals complex

Pure rotational spectra of the mercury–carbonyl sulfide complex have been observed by a pulsed-nozzle Fourier-transform microwave spectrometer, which has been recently constructed. The structure of the complex is found to be T-shaped, which is the same as the rare-gas–carbonyl sulfide complexes analogous to this system. The mercury–carbon distance and the Hg–C–O angle have been determined to be 3.7075(2) Å and 86.98(1) deg, respectively, for 202Hg–OCS from the rotational constants. Harmonic force constants of the van der Waals modes have been derived by the centrifugal distortion constants. The electric quadrupole coupling constants for 201Hg–OCS have also been determined and the values indicate small perturbation on the electric charge distribution of the mercury atom by complex formation.

Quadrupole moments of isomeric states in 213Fr and 212Fr

TDPAD measurements of electric quadrupole coupling constants were performed for high-spin isomers in 213Fr and 212Fr using single crystal Tl hosts. Using measured quadrupole moments of states in Po and At nuclei and considering explicitly the octupole vibrational coupling, a universal effective charge has been derived. Using the calculated value Q( 213 Fr( 29 2 + )) = 70 (7) e· fm 2 to determine the electric field gradient for Fr in Tl, the quadrupole moments Q( 212 Fr(15 −)) = 84 (13) e· fm 2 and Q( 212 Fr(27−)) = 173 (33) e· fm 2 are derived.

129I-Mössbauer spectroscopic study of iodide-containing chalcogenide glasses

129I-Mossbauer spectroscopy was used to study the short-range order in I-containing chalcogenide glasses. It was found that AsXI glasses, where X=S or Se, are molecular solids composed from molecular units of arsenic iodide and arsenic chalcogenide. The local environment of iodide ions in ternary superionic conducting glasses AgI−Ag2S−As2S3 is similar to that in the crystalline superionic conductor Ag3SI and differs distinctly from iodide local order in binary vitreous alloys AgI−As2S3 and crystalline AgI.129I-Mossbauer spectra of all glasses were fitted satisfactory, when a distribution of the electric-quadrupole coupling constant is taken into account.

14N quadrupole coupling in DAN and MBANP

The 14N electric quadrupole coupling constants and asymmetry parameters have been determined for the three chemically non-equivalent nitrogen sites in both 4-(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN) and (−)-2-(α-methylbenzylamino)-5-nitropyridine (MBANP) with the help of proton-nitrogen nuclear-quadrupole double resonance.

Hyperfine structure studies of niobium using laser Optogalvanic Spectroscopy.

Doppler limited Optogalvanic Spectroscopic technique is employed to study the hyperfine structure of six transitions of 93Nb. An externally stabilized single frequency ring dye laser and a commercial Nb/Ne hollow cathode lamp were used. From the observed well resolved hyperfine components of the spectra the magnetic dipole and the electric quadrupole coupling constants were evaluated. The hyperfine coupling constants for 12 levels are reported in this paper out of which values for four levels are reported for the first time. Our values are compared with the previous data wherever available.

ChemInform Abstract: The Millimeter‐ and Submillimeter‐Wave Spectrum of Boron Monofluoride: Equilibrium Structure

Abstract Utilizing a dc discharge absorption cell the millimeter and submillimeter-wave spectra of 11BF and 10BF have been observed in the v = 0, 1, 2 and v = 0, 1 vibrational states, respectively. The Dunham constants of the two isotopomers and the boron electric nuclear quadrupole coupling constant as well as the spin-rotation interaction constant of boron and fluorine have been determined. By removing from the Y01 Dunham constant the contributions due to the breakdown of the Born-Oppenheimer approximation, the resulting equilibrium bond distance is r e = 1.262672(7) A .

The millimeter and submillimeter-wave spectrum of boron monofluoride: Equilibrium structure

Utilizing a dc discharge absorption cell the millimeter and submillimeter-wave spectra of 11BF and 10BF have been observed in the v = 0, 1, 2 and v = 0, 1 vibrational states, respectively. The Dunham constants of the two isotopomers and the boron electric nuclear quadrupole coupling constant as well as the spin-rotation interaction constant of boron and fluorine have been determined. By removing from the Y 01 Dunham constant the contributions due to the breakdown of the Born-Oppenheimer approximation, the resulting equilibrium bond distance is r e = 1.262672(7) A ̊ .

Hyperfine structure of the X 2Σ + and B 2Σ + states of SrI measured by polarization spectroscopy

Microwave-optical polarization spectroscopy has been used to measure the hyperfine structure in the X 2Σ +, ν=0 state of SrI. Optical hyperfine structure in the B 2Σ +−X 2Σ +(0, 0) system was resolved by Doppler-free laser polarization spectroscopy. The magnetic dipole and electric quadrupole coupling constants were determined for the X 2Σ + and B 2Σ + states as b(X 2Σ +) = 115.93(70) MHz, b(B 2Σ +) = 2.37(70) MHz, c(X 2Σ +) = 103.29(21) MHz, eqQ(X 2Σ +) = −54.42(47) MHz and eqQ(B 2Σ +) = −84.6(86) MHz (standard errors in parentheses).

Pulsed single-mode laser ionization of hyperfine levels of zirconium-91

We identify a considerable improvement in proposed schemes for isotopic depletion of zirconium-91 on the basis of the atomic vapor laser isotope separation (AVLIS) method. The improvement lies in applying a single-longitudinal-mode dye laser for selective excitation of all hyperfine split levels of the ground state of zirconium-91. High-resolution laser-induced fluorescence spectroscopy of atomic beams of zirconium produced through laser vaporization–supersonic expansion has been used to identify transitions of zirconium with suitable hyperfine structure. Casimir magnetic-dipole and electric-quadrupole coupling constants and isotope shifts have been derived and are reported for five excited configurations. Suitable intermediate levels in a multistep resonance ionization pathway have been identified by two-color resonance ionization spectroscopy. Isotope depletion has been demonstrated on one ground-state-transition ( z F33∘←a F32at 593.7 nm) by using a specially constructed pulsed, single-longitudinal-mode dye-laser oscillator. Prospects and future directions in zirconium AVLIS are discussed.