Analysis of electromagnetic transitions in nuclei <Superscript>176, 178</Superscript>Hf

The structure of excited states and nonadiabatic effects manifested in the energies and probabilities of electromagnetic transitions are studied in the context of a phenomenological model taking into account the Coriolis mixing of the low-lying states of positive parity in rotational bands. Energies and the structure of wave functions of excited states are calculated. The calculated energies are in agreement with experimental data. The mixing effect is demonstrated to play an important role in the wave functions of vibrational states. The probabilities of E2 and M1 transitions are calculated. The theoretical values of ratios and multipole-mixing coefficients δ(E2/M1) of transitions from the first and second β and γ vibrational bands are compared with the available experimental data.     

Laser spectroscopy of the B[17.7]8-X8 and C[19.3]9-X8 transitions of holmium monochloride

Several new transitions of holmium monochloride (HoCl) have been studied at high resolution using laser excitation spectroscopy. Two main transitions, B[17.7]8-X8 and C[19.3]9-X8 have been observed and five bands, 0-0, 0-1, 1-0, 1-1, and 2-1 of the B-X transition and three bands, 0-0, 0-1, and 0-3 of the C-X transition have been obtained at high resolution and rotationally analyzed. Among several low lying states observed in dispersed fluorescence was a strong transition from the C state to a state ∼2140 cm⁻¹ above the ground state. Excitation spectra of this transition have shown that there are apparently two states, ∼6 cm⁻¹ apart. Comparison with ligand field theory calculations are consistent with assigning these states to the excited low lying Ho⁺(4f¹¹6s)Cl⁻ configuration. Several other low lying electronic states have been observed in dispersed fluorescence spectra. Although their assignments could not be established, their energies suggest that they are from the Ho⁺(4f¹⁰6s²)Cl⁻ or Ho⁺(4f¹¹6s)Cl⁻ configurations. Rotational constants have been obtained for the B[17.7]8 and C[19.3]9 states and have been used to speculate on the possible electron configurations for these states.     

High resolution measurements of hyperfine structure and isotope shifts in 9 spectral lines of Nd I

Nine transitions in Nd I, originating from various levels belonging to the 4f ⁴6s ² ground state configuration, have been studied with high resolution using an actively stabilized C.W. ring dye laser in a crossed laser-atomic-beam set-up. Accurate values for the isotope shifts in all transitions as well as for the hyperfine structure constants of 7 excited states have been obtained.     

Hyperfine structure investigations in the configuration 4f 125d6s 2 of Tm I by laser-atomic-beam spectroscopy

High resolution laser-atomic-beam spectroscopy has been applied to study the hyperfine structure of transitions starting from metastable states of the configuration 4f¹²5d6s² of Tm I. Precise values for the hyperfine constants of 8 levels belonging to the configuration 4f¹²5d6s² and 9 levels belonging to excited odd levels have been determined.     

Laser spectroscopy of the B[21.68]8-X8, B′[21.65]8-X8 and C[22.3]7-X27 transitions of holmium monofluoride

The spectrum of holmium monofluoride (HoF) in the blue (420-480 nm) region has been studied using laser-induced fluorescence. Previous work [J. Phys. B 7 (1974) L234] had assigned several bands in this region to the B8-X8 transition. By obtaining wavelength selected laser excitation spectra at high resolution and rotationally analyzing seven bands in this region, we have shown that not all the bands previously assigned to the B8-X8 system belong to the same electronic transition and have identified three separate transitions which we have labelled B8-X8, B′8-X8, and C7-X₂7. Preliminary low resolution dispersed fluorescence spectra have shown several excited states at energies greater than 4000 cm⁻¹ above the ground state and, though not all could be assigned, ligand field theory calculations are consistent with assigning them to the first excited spin-orbit component of the Ho⁺(4f¹⁰6s²)F⁻ ground state configuration or to the first excited configuration, Ho⁺(4f¹¹6s)F⁻. The results of the dispersed fluorescence experiments also tentatively place the X₂7 state at ∼70 cm⁻¹ above the ground X7 state.     

Intracavity Electronic Absorption Spectra of MoO and WO Molecules in the Visible Region

Absorption electronic spectra of MoO and WO molecules have been investigated by a intracavity laser technique in the region 550–800 run. New features have been discovered.

As for MoO molecule the rotational analysis of the four bands have been carried out for the first time. Two of these bands were referred to 0–0 transitions arisen from the new (probable triplet) low-lying electronic state, two other bands were referred to transitions arisen from excited components of X⁵II ground state.

As for WO molecule the rotational analysis of 0–0 and 1–0 bands represented A-X and B-X systems have been carried out for the first time. The new band has been discovered which has been referred to new electronic transition.

Molecular constants of new states of both molecules studied have been evaluated.     

Theoretical analysis of experimental data on 160Dy that were obtained in studying beta decay

Nonadiabatic effects manifesting themselves in the energies of excited states and in the probabilities for electric transitions in ¹⁶⁰Dy are studied on the basis of a phenomenological model of the nucleus. The energies of positive-parity low-lying states and the reduced probabilities B(E2) for both intraband and interband transitions between them are calculated. A comparison with experimental data is performed.     

Fourier transform emission spectroscopy and ab initio calculations on WO

Emission spectra of WO have been observed in the 4000-35 000 cm⁻¹ region using a Fourier transform spectrometer. Molecules were produced by exciting a mixture of WCl₆ vapor and He in a microwave discharge lamp. A ³Σ⁻ state has been assigned as the ground state of WO based on a rotational analysis of the observed bands and ab initio calculations. After rotational analysis, a majority of strong bands have been classified into three groups. Most of the transitions belonging to the first group have an Ω = 0⁺ state as the lower state while the bands in the second group have an Ω′′ = 1 state as the lower state. These two lower states have been assigned as X0⁺ and X1 spin components of the X³Σ⁻ ground state of WO. The third group consists of additional bands interconnected by common vibrational levels involving some very low-lying states. The spectroscopic properties of the low-lying electronic states have been predicted from ab initio calculations. The details of the rotational analysis are presented and an attempt has been made to explain the experimental observations in the light of the ab initio results.     

Resolved fluorescence spectra of NiH. Electronic structure,electronic energy transfer,and the Zeeman effect in low-lying states

Fourier transform spectra of collisionally induced fluorescence following isotopically selective laser excitation of NiH at ～550?nm have located an excited Ω?=?1/2 state of NiH lying 17900?cm^?1 above the electronic ground state. This is identified as v?=?0 of a ²Π_1/2 state originating from an Ni⁺ 3d⁸4s^{1 2}F configuration. Emission from this Ω′?=?1/2 state occurs predominantly to v″?=?0 and 1 of the ²Σ⁺ and W₂ ²Π_1/2 ligand field states, locating elusive f parity levels of W₂ ²Π_1/2 up to 5600?cm^?1 above the first rotational level of the electronic ground state, X ₁ ²Δ_5/2. Collisionally induced fluorescence following laser excitation at lower energies has also been recorded in the presence of a magnetic field (0.7–1?T), at Doppler limited resolution. Effective Landé factors g _J for rotational levels of the v?=?0 and 1 levels of the low-lying Ω″?=?5/2 and 3/2 components of the ²Δ and ²Π states of NiH have been derived from partially resolved Zeeman patterns. About 1600 transitions recorded in field-free conditions have been reduced to term energies relative to the lowest level of the ground state. They confirm strong spin-orbit mixing between the low-lying ligand-field states.     

A high resolution spectroscopic study of rhodium monochloride

Rhodium monochloride has been observed and characterized spectroscopically for the first time. The RhCl molecules were produced in a laser vaporization molecular beam source by the reaction of a laser vaporized rhodium plasma with CCl₄ doped in helium, and laser-induced fluorescence and dispersed fluorescence were used to study 15 of the strongest bands spanning the 535-415 nm region. Twelve of these bands were studied at high resolution using a cw ring dye laser. Two low-lying states separated by 140 cm⁻¹ have been observed. The ground state has Ω = 2 and is attributed to a ³Π_i state resulting from a δ⁴π³σ¹ electronic configuration. The other low-lying state has Ω = 3 and is attributed to a ³Δ_i state resulting from a δ³π⁴σ¹ electronic configuration. Excited states with Ω values ranging from 1 to 4 have been observed. Dispersed fluorescence from these excited levels has been used to identify a large number of low-lying electronic states within an energy range of 5200 cm⁻¹ and has also been used to determine a ground state vibrational frequency of ∼348 cm⁻¹. Λ-doublings have been observed in all the transitions studied at high resolution.     

Sm原子的偶宇称高激发态的光谱研究

采用双色三步激发和光电离过程,对Sm原子的偶宇称高激发态的光谱进行了研究.先采用两条激发路线分别将Sm原子两步共振激发至待测的高激发态,然后利用光电离技术对其进行探测.分别将第一束激光的波长固定在627.50nm和624.41nm上,以便将Sm原子从亚稳态共振激发到由4f⁶6s6p电子组态所构成的两个原子状态上.第二束激光在440-700nm的波段范围内扫描,不仅使Sm原子在30040-38065cm^-1能域内的偶宇称高激发态上布居,将其进一步光电离,测量了其光谱.通过光谱定标和选择定则等分析手段,本工作不仅精确获得了136个态的能级位置,而且也唯一确定了其总角动量,并且给出了相关跃迁的相对谱线强度.     

Intrinsic states and rotational bands in 176Ta and 178Ta

High-spin states in the deformed, doubly odd nuclei, ¹⁷⁶Ta and ¹⁷⁸Ta have been studied by time-correlated γ-ray and electron spectroscopy techniques following (HI,xn) reactions. The new results independently confirm and extend in spin the previously known two- and four-quasiparticle states, albeit with some differences. Many high-seniority structures, most of them with associated rotational bands, have been identified for the first time. Several high-K isomers with half-lives ranging from a few nanoseconds up to hundreds of milliseconds have been discovered. Observation of rotational bands, built upon the intrinsic states has allowed characterization of the configurations, through both the in-band decay properties and alignments. The excitation energies of the observed multi-quasiparticle structures are generally reproduced using calculations based on the Lipkin-Nogami pairing model with inclusion of the effects of blocking and empirical nucleon-nucleon interactions. Some discrepancies in the energies, such as for the 14⁻ and 15⁻ isomers in ¹⁷⁶Ta and ¹⁷⁸Ta, respectively, are attributed to specific configuration mixing. Several anomalously fast K-forbidden transitions are discussed.     

Identification of excited singlet states of chlorophenol isomers

The UV spectra of optical absorption of para-, meta-, and ortho-chlorophenol are recorded in the gas phase. The bands of UV spectra are assigned to the electronic transitions of molecules to definite excited singlet states on the basis of calculations by the TDDFT B3LYP/6-311++G(d, p) method. In each case the electron configuration making the predominant contribution to the particular singlet state is determined. The energies of singlet electronic transitions are shown to depend on the energy spacing between the molecular orbitals involved in these transitions.     

A study of the (3He,n) reaction on isotopes of tin

The (³He, n) reaction has been studied on^{112,116,118,120,124}Sn at 25.4 MeV. Angular distributions were measured over the range 0°–25° and the results compared with predictions of zero-range DWBA calculations. In addition to the around-state transitions, L = 0 transitions were also observed to low-lying states in every case. Simple two component wave functions, as well as those obtained from a more sophisticated pairing model, are compared with the data in order to explain the appearance of the anomalously low-lying excited 0⁺ states observed. L = 2 transitions were observed to low-lying 2⁺ states, but the strength of these transitions was much less than expected from the systematics of (t, p) results for N = 50 nuclei.     

Collective and two-quasiparticle states in 158Gd observed through study of radiative neutron capture in 157Gd

The level structure of ¹⁵⁸Gd has been studied using the prompt γ-rays and conversion electrons emitted following neutron capture in ¹⁵⁷Gd. The γ-ray energy and intensity measurements were made using both Ge(Li) detectors and a curved-crystal spectrometer. Conversion-electron energy and intensity measurements were made using two separate magnetic spectrometers: one to measure the primary electron spectrum and the other to measure the lower energy secondary electron spectrum. Some γ-γ coincidence measurements were also made among the secondary γ-rays. From these data, a neutron separation energy of 7937.1 ± 0.5 keV has been determined for ¹⁵⁸Gd. A level scheme containing 59 excited states with energies < 2.25 MeV, for which de-excitation modes have been identified, is proposed for ¹⁵⁸Gd. Many of these states have been grouped into rotational bands. A total of thirteen excited rotational bands with band-head energies below 2.0 MeV are contained in the level scheme. Features of the proposed level scheme include: the K^π = 0^?, 1^? and 2^? octupole-vibrational bands with band-head energies of 1263, 977 and 1793 keV, respectively; the γ-vibrational band at 1187 keV; three excited K^π = 0⁺ bands with band-head energies of 1196, 1452 and 1743 keV; several two-quasiparticle bands with band-head energies in keV (and K^π assignments) of 1380 (4⁺), 1636 (4^?), 1847 (1⁺), 1856 (1^?), 1920 (4⁺) and 1930 (1⁺). An analysis of (d, p) reaction data is presented which permits definite two-quasiparticle configuration assignments to be made to most of these latter bands. Evidence is presented which suggests strong mixing of some two-neutron and two-proton bands. A phenomenological four-band mixing analysis is made of the energy and E2 transition-probability data for the ground-state band and the three lowest-lying excited collective positive-parity bands. Good agreement with experiment is obtained. A Coriolis-mixing analysis of the octupole bands has been carried out and good agreement with the data on level energies and E1 transition probabilities to the ground-state band has been achieved. Values of Z, the ratio of the E1 transition matrix element with ΔK = 1 to that with ΔK = 0, involving the octupole bands and the first four 0⁺ bands are derived. For three of these 0⁺ bands, absolute values of these matrix elements are deduced. An interesting alternation in the sign of Z is observed for these four 0⁺ bands.     

A high resolution study of the transitions 4f 76s 2→4f 76s6p in the Eu I-spectrum

Eight transitions in the Eu I-spectrum connecting the ground state with configuration 4f ⁷ 6s ² with states of the configuration 4f ⁷ 6s6p were studied with high resolution laseratomic-beam spectroscopy. CW dye lasers operating in the wavelength regions 435–470 nm and 560–630 nm were used for this study. New data for the hyperfine structure in¹⁵³Eu were obtained as well as new and more accurate values for the isotope shifts between¹⁵¹Eu and¹⁵³Eu. The existing data for the hyperfine structure in¹⁵¹Eu were reproduced with an exception for the levelz ⁶ P _7/2.     

Polarization labeling spectroscopy of NO2

Polarization-labeling spectroscopy is used to simplify the visible spectrum of nitrogen dioxide. Nonlinear polarization effects are used to label and probe molecules in selected rotational-vibrational levels. Those labeled molecules can be detected by their depolarizing effect on a probe laser. The resulting spectra are considerably less complicated than normal absorption spectra. P- and R-branch transitions can be readily identified, and approximate excited-state rotational constants are determined. With more powerful lasers, it may be possible to use polarization labeling to unravel the very complicated vibrational structure of the NO₂ excited states.     

Two-photon spectroscopy of ytterbium

Two-photon laser spectra of the Yb vapor have been obtained. Transitions to highly excited 4f¹⁴ 6sns¹S₀ and 4f¹⁴ 6snd ¹D₂ states are seen in direct two-photon excitation. Hybrid resonances involving 4f¹⁴ 6s6p ¹P⁰₁ and 4f¹⁴ 5d6s ³D₂ intermediate states lead to transitions to 4f¹⁴ 6sns¹S₀, 4f¹⁴ 6snp ³P⁰_2,1 and 4f¹⁴ 6snd ¹D₂ levels.     

Alpha cluster states in 16O

A very successful cluster-core model for the rotational bands of light nuclei has been extended to treat excited core states. The resulting coupled-channels problem has been solved for the ${}^{16}\text{O }{}^{12}\text{C + α}$ system. As well as the known + ve and ? ve parity bands many new levels are predicted and compared with experiment. The agreement between theory and experiment is very good both for the excitation energies and the decay properties. We predict the positions of two low-spin non-natural parity levels with E_x < 20 MeV and the positions of many high-spin states. In particular, we explain why the 8⁺ level seen in α-transfer at 22.5 MeV could not be found in the α-scattering cross sections and predict a second 8⁺ at 24.4 MeV. We discuss how the levels may be regarded as members of rotational bands and determine the terminating J-values for these bands. Finally we show that the usual rotational model would be a poor approximation for the cluster bands of ¹⁶O.     

Influence of excited configurations on the intensities of electric-dipole transitions of rare-earth ions

The theory of induced electric-dipole transitions of rare-earth ions in crystals and glasses is improved by taking into account the third-order effects of perturbation theory with respect to the energies of virtual excitations of 4f electrons to the 5d states. Since the energy regions of excited 4f ^{N ? 1}5d states are usually superimposed with the charge-transfer bands, the effects caused by a virtual transfer of an electron from the outer shells of ions of the surroundings (ligands) to the unfilled 4f ^N shells are also considered. The Pr³⁺, Sm³⁺, and Eu³⁺ ions are considered as examples. It is found that some difficulties inherent in the Judd-Ofelt calculation scheme are successfully overcome. The agreement of the calculated results with the experimental data improves.