Investigation of the hyperfine structure of TaI-lines

The hyperfine structure of several spectral lines of the neutral tantalum atom was investigated by means of saturated optogalvanic laser spectroscopy. From the spectra, we have determined the magnetic hyperfine interaction constants A and the electric quadrupole interaction constants B of 14 levels with even parity and 23 levels of odd parity.     

Hyperfine structure studies of Tantalum

A narrow bandwidth ring dye laser pumped by an argon ion laser has been used to investigate the hyperfine structure of the even and odd parity levels of tantalum by optogalvanic spectroscopy in the wavelength range 5640 to 6050 Å. Seventeen transitions have been observed and eight of these have not been reported in the literature so far. These transitions involve 27 levels with 15 odd and 12 even parity configurations. The magnetic dipole hyperfine interaction constants A and the electric quadrupole interaction constants B for these levels have been computed and compared with the data available in literature. The results for the levels at 34799.71 cm^?1, 26960.46 cm^?1 and 19657.78 cm^?1 are reported for the first time.     

Investigation of the hyperfine structure of Ta I-lines (III)

By investigating the hyperfine structure of 41 Ta I lines we could determine the magnetic hyperfine interaction constants A and the electric quadrupole interaction constants B of 25 even parity levels and 32 odd parity levels. Additionally, we could classify one line. With 78 dipole allowed transitions which we tried to excite by laser light we obtained neither optogalvanic nor fluorescence signals. Therefore we conclude that some of the Ta I levels, listed in commonly used tables [e.g. Moore, Ch.: Atomic energy levels. Vol. III. Natl. Bur. Stand. (U.S.) Circ. No. 467. Washington, D.C.: U.S. GPO 1949], do not exist.     

Electron attachment and vibrational excitation in hydrogen iodide: calculations based on the nonlocal resonance model

High resolution laser spectroscopy has been applied to study the hyperfine structure of excited energy levels of Thulium I. As part of our aim to complete the fine and hyperfine structure of the Tm I spectra 51 transitions in the visible were measured and precise values for the magnetic dipole hyperfine structure constants A of 24 odd and 19 even levels were determined. In addition, a new energy level of even parity with J = 3/2 is found at 27 509.40 (5)cm^?1 using laser induced fluorescence spectroscopy.     

High resolution spectroscopy of methyltrioxorhenium: towards the observation of parity violation in chiral molecules

Originating from the weak interaction, parity violation in chiral molecules has been considered as a possible origin of biohomochirality. We have proposed the observation of molecular parity violation using the two-photon Ramsey fringes technique on a supersonic beam. As a first step in this direction, a detailed spectroscopic study of methyltrioxorhenium (MTO) has been undertaken. It is an ideal test molecule as the achiral parent molecule of chiral candidates for a parity violation experiment. For the (187)Re MTO isotopologue, a combined analysis of Fourier transform microwave and infrared spectra as well as ultra-high resolution CO(2) laser absorption spectra enabled the assignment of 28 rotational lines and 71 rovibrational lines, some of them with a resolved hyperfine structure. A set of spectroscopic parameters in the ground and first excited state, including hyperfine structure constants, was obtained for the ν(as) antisymmetric Re=O stretching mode of this molecule. This result validates the experimental approach to be followed once a chiral derivative of MTO is synthesized, and shows the benefit of the combination of several spectroscopic techniques in different spectral regions, with different set-ups and resolutions. The first high resolution spectra of jet-cooled MTO, obtained on a set-up being developed for the observation of molecular parity violation, are shown, which constitutes a major step towards the targeted objective.     

Fine-structure analysis of the (5d+6s)5 levels of Ta I

The fine structure of the prominent even levels of the neutral tantalum atom has been analyzed by simultaneous parametrization of one- and two-body interactions for the model space (5d+6s)⁵. The analysis was stimulated by the current discovery of several energy levels. It was possible to clear the configurations and designations of the energy levels given in commonly used tables. Magnetic-dipole hyperfine interaction constants A and electric-quadrupole hyperfine interaction constants B were calculated using the calculated eigenfunctions and adjusting radial integrals in a least-squares procedure which compares the calculated Aand B-constants with the experimental values. The rms error of this fitting procedure confirms the quality of the fine structure analysis. Moreover, wavenumbers and hyperfine constants of 52 further levels, up to now unidentified, are predicted.     

Test of advanced hyperfine structure theory by precision radio-frequency and laser spectroscopy in molybdenum

The hyperfine structure splittings of 32 even parity states and of 26 odd partity states of molybdenum have been measured by atomic beam magnetic resonance and by laser induced fluorescence. The analysis of the hyperfine structure data of the even parity configurations (4d+5s)⁶ yields experimental evidence for second order hyperfine interactions. In addition, theg _J factors of 19 fine structure levels have been determined in order to test the quality of intermediate coupling wave functions for the (4d+5s)⁶ configurations.     

Hyperfine splitting of the odd 4 F J o , 2 P J o and 4 S J o LaI multiplets

High resolution spectra of LaI lines recorded in the R6G region by laser-induced resonance fluorescence method show well resolved hyperfine structures. The analysis of the hyperfine structure of seven LaI transitions is presented here. It has allowed the deduction of magnetic dipole and electric quadrupole constants of all levels belonging to the excited odd parity multiplets: ⁴ F ^o (J = 3/2-9/2), ² P ^o (J = 1/2,3/2), and ⁴ S ^o (J = 3/2). Some of the results are new and some of them present improved values of the hyperfine splitting constants.     

Determination of the proton tunneling splitting of the vinyl radical in the ground state by millimeter-wave spectroscopy combined with supersonic jet expansion and ultraviolet photolysis

The vinyl radical in the ground vibronic state produced in a supersonic jet expansion by 193 nm excimer laser photolysis of vinyl bromide was investigated by millimeter-wave spectroscopy. Due to the proton tunneling, the ground state is split into two components, of which the lower and higher ones are denoted as 0+ and 0-, respectively. Eight pure rotational transitions with Ka = 0 and 1 obeying a-type selection rules were observed for each of the 0+ and 0- states in the frequency region of 60-250 GHz. Tunneling-rotation transitions connecting the lower (0+) and upper (0-) components of the tunneling doublet, obeying b-type selection rules, were also observed in the frequency region of 190-310 GHz, including three R- and six Q-branch transitions. The observed frequencies of the pure rotational and tunneling-rotation transitions were analyzed by using an effective Hamiltonian in which the coupling between the 0+ and 0- states was taken into account. A set of precise molecular constants was obtained. Among others, the proton tunneling splitting in the ground state was determined to be DeltaE0 = 16,272(2) MHz. The potential barrier height was estimated to be 1580 cm(-1) from the proton tunneling splitting, by an analysis using a detailed one-dimensional model. The spin-rotation and hyperfine interaction constants were also determined for the 0+ and 0- states together with the off-diagonal interaction constants connecting the 0+ and 0- states, epsilonab + epsilonba for the spin-rotation interaction and Tab for the hyperfine interaction of the alpha (CH) proton. The hyperfine interaction constants, due to the alpha proton and the beta (CH2) protons, are consistent with those derived from electron spin resonance studies.     

Hyperfine structures of the 2 (3)Sigma(g) (+), 3 (3)Sigma(g) (+), and 4 (3)Sigma(g) (+) states of Na(2)

The hyperfine structures of the 2 (3)Sigma(g) (+), 3 (3)Sigma(g) (+), and 4 (3)Sigma(g) (+) states of Na(2) have been resolved with sub-Doppler continuous wave perturbation facilitated optical-optical double resonance spectroscopy via A (1)Sigma(u) (+) approximately b (3)Pi(u) mixed intermediate levels. The hyperfine patterns of these three states are similar. The hyperfine splittings of the low rotational levels are all very close to the case b(betaS) limit. As the rotational quantum number increases, the hyperfine splittings become more complicated and the coupling cases become intermediate between cases b(betaS) and b(beta J) due to spin-rotation interaction. We present a detailed analysis of the hyperfine structures of these three (3)Sigma(g) (+) states, employing both case b(betaS) and b(beta J) coupling basis sets. The results show that the hyperfine splittings of the (3)Sigma(g) (+) states are mainly due to the Fermi-contact interaction. The Fermi contact constants for the two d sigma Rydberg states, the 2 (3)Sigma(g) (+) and 4 (3)Sigma(g) (+), are 245+/-5 MHz and 225+/-5 MHz, respectively, while the Fermi contact constant of the s sigma 3 (3)Sigma(g) (+) Rydberg state is 210+/-5 MHz. The diagonal spin-spin and spin-rotation constants, and nuclear spin-electronic spin dipolar interaction parameters of the 3 (3)Sigma(g) (+) and 4 (3)Sigma(g) (+) states are also obtained.     

The effect of symmetry restrictions upon the hyperfine properties

The effect of spatial symmetry restrictions upon the calculated values of the hyperfine splitting constants is examined and results are reported for B, C, O and F. It is found that, if no symmetry restrictions are placed upon the unrestricted Hartree-Fock orbitals, the resulting hyperfine constants (except spin densities) are in good agreement with experiment and with configuration interaction calculations. Nuclear magnetic moments and quadrupole moments are reported on the basis of these calculations and the observed hyperfine structure.     

A new energy level of the neutral tantalum atom

Investigating the hyperfine structure (hfs) of the not yet classified line λ=4160.99 Å we succeeded in the determination of the electronic angular momenta of the combining levels and in the identification of the lower level using the hfs constants of all known levels as a finger-print card-index. In this way the lower level turned out to be thea ² G _9/2 level, which has even parity. Using the energy of this level and the wavenumber of the transition it was possible to determine the energy of the (odd parity) upper level to 34716.23 ± 0.02 cm^?1. The total angular momentum quantum number amounts toJ=11/2. Additionally, it was possible to identify the line λ=3436.00 Å as a further combination with this new level.     

Parameterization of the hyperfine structure of metastable states in103Rh

The experimental data on the hyperfine structure of metastable even parity states in¹⁰³Rh have been analysed by means of an effective-operator formalism. The effective radial parameters of the magnetic dipole interaction are determined, using wave functions in intermediate coupling. The comparison with relativistic calculations gives an estimate of the effects due to configuration interaction.     

The interpretation of molecular magnetic hyperfine interactions

Investigations of the hyperfine structure in the excited electronic states of several free radical species have revealed shortcomings in the currently accepted values used for the theoretical interpretation of such interactions. We introduce updated reference atomic values from a combination of experimental observations and ab initio calculations. The latter are at Hartree-Fock and multireference configuration interaction levels of theory and several atomic test cases are discussed. Furthermore, ground and excited electronic state hyperfine coupling constants are calculated using both levels of theory for a range of first- and second-row diatomic hydride and nonhydride radicals. These results, together with a selection of other experimental measurements are then compared with experimental data where available, and the implications of the revised interpretation are discussed.     

Saturation spectroscopy of BO2 at 5145 Å

The hyperfine structure of one of the transitions of BO₂ coincident with the 5145 Å argon-ion laser line has been resolved by the technique of intermodulated fluorescence. The splitting has been interpreted in terms of the hyperfine constants of the excited A ²Π_u electronic state.     

Spectral simulation and interpretation of LiZn and LiCd blue-green emission

Magnetic hyperfine interaction constants (A factors) have been determined for nine levels in the 4d5s and 4d5p configurations of the Y⁺ ion by Doppler-free saturation spectroscopy and level crossing spectroscopy in a sputtered vapour.     

Superfine and hyperfine structures in the v3 band of 32SF6

We present a first detailed account of our theoretical approach to reproduce observed superfine and hyperfine structures in the ν₃ band of SF₆ and we display various observed and calculated patterns of superfine clusters exhibiting hyperfine effects. The main operators of the hamiltonian are derived and the associated constants are related to molecular parameters. We show that, owing to the off-diagonal terms in the hyperfine hamiltonian, a mixing occurs between vibration—rotation states with different point-group symmetry species. As a consequence, superfine and hyperfine structures have to be considered simultaneously and hyperfine hamiltonian matrices connecting several vibration—rotation states need to be diagonalized to reproduce the spectra. We analyse in greater detail a few typical examples from which several molecular constants have been determined (e.g. t₀₄₄, c_d). For the first time, the sign c_d is obtained. Also an effective change, Δc_d, is found between upper and lower levels which can be readily interpreted as a manifestation of the tensor spin—vibration interaction.     

Theoretical studies of alkyl radicals in the NaY and HY zeolites

Interplay of quantum mechanical calculations and experimental data on hyperfine coupling constants of ethyl radical in zeolites at several temperatures was engaged to study the geometries and binding energies and to predict the temperature dependence of hyperfine splitting of a series of alkyl radicals in zeolites for the first time. The main focus is on the hyperfine interaction of alkyl radicals in the NaY and HY zeolites. The hyperfine splitting for neutral free radicals and free radical cations is predicted for different zeolite environments. This information can be used to establish the nature of the muoniated alkyl radicals in the NaY and HY zeolites via muSR experiments. The muon hyperfine coupling constants of the ethane radical cation in these zeolites are very large with relatively little dependence on temperature. It was found that the intramolecular dynamics of alkyl free radicals are only weakly affected by their strong binding to zeolites. In contrast, the substrate binding has a significant effect on their intermolecular dynamics.     

Polarization quantum beat spectroscopy of HCF(A1A"). I. 19F and 1H hyperfine structure and Zeeman effect

To further investigate the (19)F and (1)H nuclear hyperfine structure and Zeeman effect in the simplest singlet carbene, HCF, we recorded polarization quantum beat spectra (QBS) of the pure bending levels 2(0) (n) with n = 0-7 and combination bands 1(0) (1)2(0) (n) with n = 1-6 and 2(0) (n)3(0) (1) with n = 0-3 in the HCF A(1)A(")<--X(1)A(') system. The spectra were measured under jet-cooled conditions using a pulsed discharge source, both at zero field and under application of a weak magnetic field (<30 G). Analysis yielded the nuclear spin-rotation constants C(aa) and weak field Lande g(aa) factors. Consistent with a two-state model, the majority of observed vibrational levels exhibit a linear correlation of C(aa) and g(aa), and our analysis yielded effective (a) hyperfine constants for the (19)F and (1)H nuclei (in MHz) of 728(23) and 55(2), respectively. The latter was determined here owing to the high resolving power of QBS. The vibrational state selectivity of the (19)F hyperfine constants is discussed, and we suggest that the underlying Renner-Teller interaction may play an important role.     

Millimeter-wave spectroscopy of H(2)C=CD: Tunneling splitting and ortho-para mixing interaction

The H(2)C=CD isotopic species of vinyl radical produced in a supersonic jet expansion by ultraviolet laser photolysis was studied by millimeter-wave spectroscopy. Due to the tunneling motion of the α deuteron, the ground state is split into two components, 0(+) and 0(-). Tunneling-rotation transitions connecting the lower (0(+)) and upper (0(-)) components of the tunneling doublet were observed in the frequency region of 184-334 GHz, including three R- and two Q-branch transitions. Three and two pure rotational transitions in the K(a)=0 and 1 stacks, respectively, were also observed for each of the 0(+) and 0(-) states in the frequency region of 52-159 GHz. Least-squares analysis of the observed frequencies for the tunneling-rotation and pure rotational transitions with well resolved hyperfine structures yielded a set of precise molecular constants, among which the tunneling splitting in the ground state was determined to be ΔE(0)=1187.234(17)?MHz, which is 1/14 that for H(2)C=CH. The potential barrier height derived from the observed tunneling splitting by an analysis of the tunneling dynamics using a one-dimensional model is 1545?cm(-1), consistent with the value 1568?cm(-1) obtained for the normal vinyl. The observed spectrum was found to be perturbed by a hyperfine interaction connecting ortho and para levels. The constant for the interaction, which we call the ortho-para mixing Fermi contact interaction, has been determined to be δa(F) ((β))=68.06(53)?MHz. This is believed to be the first definite detection of such an interaction. By this interaction the ortho and para states of H(2)C=CD are mixed up to about 0.1%. The constant is more than 1000 times larger than spin-rotation interaction constants that cause ortho-para mixing in closed shell molecules and suggests extremely rapid conversion between the ortho and para nuclear spin isomers of H(2)C=CD.