Zeeman effect of atomic uranium in the high lying odd levels measured by laser induced fluorescence spectroscopy

We measured Zeeman effect of atomic uranium spectra using laser induced fluorescence spectroscopy, and derived the J-value and g-factor of the second step levels. J-values and g-factors of high lying odd levels could be obtained. These data, especially the g-factors, have almost been unknown so far. We could verify our method which can be useful to measure J-values and g-factors of high lying levels of complex atoms like uranium. Received 27 July 1999 and Received in final form 30 November 1999     

In-source spectroscopy on astatine and radium for resonant laser ionization

At on-line isotope separator facilities, rare isotopes of radioactive elements such as astatine, radium or polonium are demanded for fundamental research on nuclear structure. These elements are generally suitable for a resonance ionization laser ion source, but more data on the atomic structure is necessary to develop efficient laser ionization schemes. Due to the missing stable reference isotopes spectroscopic investigation of the atomic structure can only be performed during on-line operation. At the Isotope Separator and ACcelerator (ISAC) facility at TRIUMF, the elements astatine and radium were investigated by in-source laser spectroscopy to optimize the laser ionization efficiency. For astatine, laser spectroscopy was performed to search for high lying bound states as well as for auto-ionizing resonances. This led to the identification of four new high lying bound states of odd parity, while no auto-ionizing resonances were observed in the investigated region. Furthermore, the feasibility and the impact of laser ionization on the yield of radium isotopes was investigated using an activated target after proton irradiation.     

基于激光共振电离质谱的钆奇宇称高激发态研究

钆同位素可作为生产医用同位素¹⁶¹Tb等的靶材,受限于高效光电离路径缺失等问题,目前仅能通过电磁方法生产,为实现钆的多步光电离,需要获取高激发态等光谱数据.基于国内自主研发的高分辨激光共振电离质谱,利用双色三步光电离方案,扫描了钆的36900～37700 cm^-1能区,首次获取了7条奇宇称高激发态能级,能级位置准确度可达±0.1 cm^-1,并根据角动量选择定则确定了可能的J值,同时发现了可用于质谱性能检验的单色光电离谱线.     

Continuous scanning of atomic uranium levels

A simple, efficient method of uncovering and assigning high levels of atomic uranium is presented. 62 new levels have been discovered in the region 33 580–34 400 cm^?1. The experimental system is especially suitable for spectroscopic measurement of complex atoms.     

Two-step single-colour photoionization spectroscopy of atomic uranium

The single-colour photoionization spectrum of atomic uranium is recorded in the spectral region from 366 to 371 nm. Most of the 43 observed resonances are found to be associated with the two-step photoionization process. Based on known energy levels seven new transitions have been proposed. Three of these transitions originate either from the ground state or the lowest metastable state at 620 cm^–1.     

Thermal photoionization in resonance ionization spectroscopy

In Resonance Ionization Spectroscopy, neutral atoms are usually produced by thermal effects, using an oven or a hot surface at high temperature. The radiation from these thermal sources is intense enough to effectively contribute to the photoionization of atoms excited by laser pumping. We show that, for the most common experimental conditions, the ratio of thermal to laser photoionization can be higher than one for excited levels which lie as far as a few thousand cm^–1 below the ionization threshold. This result is obtained with the use of the analytic expression for the photoionization cross-section of a hydrogen-like atom. We suggest two applications of this thermal photoionization. Namely, the study of highly excited states and Quasi Resonance Ionization Spectrometry, using only one laser of low radiance.Commissariat à l'Energie Atomique, Centre d'Etudes Nucléaires de Fontenay-aux-Roses DERDCA/DCAEA/SEA, BP no 6, F-92265 Fontenay-aux-Roses Cedex, France (Visiting scientist at Ecole Polytechnique from Commissariat à l'Energie Atomique)Commissariat à l'Energie Atomique, Centre d'Etudes Nucléaires de Saclay, IRF/DPHG/PAS. Bât 462, F-91191 Gif-sur-Yvette Cedex, France     

Doppler-free two-photon laser spectroscopy of barium I: Hyperfine splitting and isotope shift of high lying levels

The Doppler-free two-photon absorption method performed with a narrowbandc w dye laser permitted high resolution measurements of transitions from the Ba I ground state 6s ^{2 1} S ₀ to several highly excited states. The lifetimes and hyperfine splittings of these states as well as the isotope shifts of the transitions have been determined accurately. The lifetime values are in agreement with transition probability data; the hyperfine splitting results show considerable configuration interaction effects. A detailed discussion of the isotope shifts is given.     

Low lying energy levels of CsFeCl3

Submillimeter wave ESR has been performed to investigate the singlet ground state and the first excited doublet of the quasi-1D hexagonal magnet CsFeCl₃ at 4.2 K. Using backward travelling wave tubes of 220 GHz and 370 GHz bands combined with pulsed magnetic fields up to 10 T, we succeeded in observing all five possible transitions for H//c and HIc for the first time. The results suggest that the single ion model is not applicable to this system in order to interpret all the absorption lines observed in our experiment.     

Spontaneous noise spectroscopy of an atomic magnetic resonance

We have experimentally demonstrated a new type of noise spectroscopy, which requires neither amplitude nor frequency noise of the light source. A highly stabilized diode laser provides low-noise light for the optical magnetic resonance of Rb atoms. The laser light transmitted through the Rb vapor contains significant intensity fluctuations whose power spectrum has a distinct peak at the Larmor frequency. The fluctuations are spontaneously generated by the atoms and are attributed to the stochastic properties of the photon scattering which randomly interrupts the Larmor precession of the atomic magnetic moment.     

Laser developments and resonance ionization spectroscopy at IGISOL

We present an overview of recent laser ion source developments at the IGISOL facility, Jyväskylä. Technological advances in the lasers have led to a considerable increase in second-harmonic laser power with the use of intra-cavity second-harmonic generation, as well as to narrow linewidth capability by applying an injection-locking technique to a Ti:sapphire laser. The use of a diffraction grating for frequency selection in a new laser resonator has dramatically improved the wide-range tunability of the laser system, resulting in an ideal tool for the development of new ionization schemes. The role of different laser bandwidths, laser intensity and environmental broadening mechanisms on the experimental width of the measured spectral line have been studied using bismuth, silver and nickel, in the gas cell and expanding gas jet. Applications of novel ion guide nozzle design has led to remarkably collimated gas jets which overcome the current limitations in the gas cell-based laser ion source trap (LIST) method. Detailed planning is under way to optimize the new laser laboratory and laser transport path in order to fully exploit the unique opportunities afforded by the new IGISOL-4 facility.     

Two colour multiphoton ionization spectroscopy of uranium from a metastable state

Using two pulsed tunable dye lasers, a two colour multiphoton ionization process has been utilised to explore the higher energy levels of uranium. One hundred and thirty eight new UI levels have been observed in the 37540–38420 cm^–1 region. J assignments of these levels have been suggested on the basis of their excitation from intermediate levels with known and contiguous J values. In eight cases the J assignments are unique.     

Environmental effects on atomic energy levels

This paper considers environmental effects both on the ground-state charge distribution and on the different energy levels of a hydrogen atom. The medium is represented by a continuous dielectric, and the effect of the polarization of this medium is computed, using both a simplified self-consistent-field variational treatment, and also a perturbation calculation. The dielectric effects of the medium are compared with similar results based on discrete molecular models, taking into account both dispersion and overlap-repulsion forces. The dielectric effects on the ground-state charge distribution are of the same order of magnitude as the effects due to dispersion forces. The dielectric effects on Rydberg-type electronic transitions lead to blue shifts. This conclusion is in agreement with some recent experimental results.     

K-shell ionization by high energy electrons

It is shown that the data of Middleman, Ford and Hofstader on K-shell ionization by electrons with energy from 150 to 900 MeV is fit very well by a relativistic form of Bethe's theory of ionization.     

Stark spectroscopy of high-lying odd parity levels in atomic samarium

We have performed a series of experiments to observe 11 Stark-induced E1 transitions from the 15650.55 cm^-1 level to higher levels with odd parity in samarium (Sm) with optical double-resonance technique. Five Stark-induced E1 transition to the 28233.08, 28613.22, 28913.97, 29041.31 and 29130.03 cm^-1 levels have been observed. In order to investigate the contributors to the Stark-induced E1 transition, we have measured scalar and tensor polarizabilities for the observed Stark-induced E1 transitions. Clear Stark splittings were observed for the levels 28233.08 and 28613.22 cm^-1, and their tensor polarizabilities were determined for each isotope. Scalar polarizabilities were determined for the 28233.08, 28613.22, 28913.97 and 29130.03 cm^-1 levels for the first time. Among them, scalar polarizability for the 28233.08 cm^-1 level was the largest in magnitude and was 3.60(10) x 10³ kHz/(kV/cm)² for Sm. We noticed that both scalar and tensor polarizabilities of the 28233.08 cm^-1 level depend on the isotope; the difference of magnitude of the scalar and tensor polarizabilities between Sm and Sm were remarkably large and were about 10 and 6 percent, respectively.Received: 10 February 2003, Published online: 30 July 2003PACS: 32.60.+i Zeeman and Stark effects - 32.10.Dk Electric and magnetic moments, polarizabilityD. Angom: Present address: Physical Research Laboratory, Navarangpura, Ahmedabad 380 009, India.     

Low lying energy levels of56Fe from γ-γ coincidences

The level scheme of⁵⁶Fe was built up from γ-γ coincidence measurements using Ge(Li) detectors and a Dual Parameter data collection system. The previously suggested γ-transitions [8] of 263.3, 410.9, 485.2, 674.7 and 1,462.3 keV were confirmed and evidence found for a new 655.0 keV γ-transition between the levels at 4,100.32 and 3,445.32 keV. No evidence was found for the transition of 2,657.4 keV and the previously proposed β⁺-feeding of the level at 3,600.3 keV is ruled out, while the existence of a level at 4,447.5 keV is suggested. The relative intensities and branching ratios of 44 transitions were determined. A calculation of experimentalK-shell internal conversion coefficients α(K) showed large discrepancies from previous studies for the 3,009.6 and 3,451.2 keV transitions, the latter being assigned a different multipolarity. Logft values were calculated and spins and parities of the levels deduced. In particular the assignment of 3⁺ is verified for the level at 4,297.97 keV.     

高纯锗中浅受主的光热电离光谱

在液氦温度附近, 运用傅里叶变换光谱以及与之相连的磁光光谱系统, 对室温电阻率约为50Ω·cm的p型高纯锗样品进行了高灵敏度的光热电离光谱的研究.从实验上确定了高纯锗样品中浅杂质光热电离的最佳温度范围, 在该温度范围内测量了样品的光热电离光谱, 指出该样品中主要杂质为浅受主硼与铝. 对杂质谱线发生分裂的两种原因, 补偿性杂质导致的快速复合以及随机应力等, 进行了分析讨论. 关键词： 高纯锗 光热电离光谱 元素半导体中的杂质和缺陷能级     

Four-photon spectroscopy of deep energy levels in CdS

Deep levels in a II–VI compound are investigated using a resonant non-degenerate four-photon mixing method, at a low sample temperature. Experimental evidence of deep levels in an undoped CdS is obtained. Amplitude as well as polarization dispersion of the coherent signal output is studied by scanning the 2 _d — ₂ frequency near the midgap resonances at 13700, 15480 and 15700 cm^–1. Measurement of impurity content in the crystal is discussed.     

高纯锗中浅受主的光热电离光谱

在液氦温度附近, 运用傅里叶变换光谱以及与之相连的磁光光谱系统, 对室温电阻率约为50Ω·cm的p型高纯锗样品进行了高灵敏度的光热电离光谱的研究.从实验上确定了高纯锗样品中浅杂质光热电离的最佳温度范围, 在该温度范围内测量了样品的光热电离光谱, 指出该样品中主要杂质为浅受主硼与铝. 对杂质谱线发生分裂的两种原因, 补偿性杂质导致的快速复合以及随机应力等, 进行了分析讨论.     

Study of the energy response of high pressure ionization chamber for high energy gamma-ray

The energy response calibration of the commonly used high pressure ionization chamber is very difficult to obtain when the gamma-ray energy is more than 3 MeV.In order to get the calibration of the higher part of the high pressure ionization chamber,we use the Fluka Monte Carlo program to perfclrm the energy response in both the spherical and the cylindrical high pressure ionization chamber which are full of argon gas.The results compared with prior study when the gamma-ray energy is less than 1.25 MeV.Our result of Monte Carlo calculation shows agreement with those obtained by measurement within the uncertainty of the respective methods.The calculation of this study is significant for the high pressure ionization chamber to measure the high energy gamma-ray.