Hyperfine structure in the atomic spectrum of niobium

A parametric analysis of the fine and the hyperfine structure for the three even configurations 4d^45s, 4d ⁴5s ² and 4d⁵ has been performed. Effective one-electron parameters a _nl ^kskl(k _s k _l = 01, 12 and 10) and b _nl ⁰² were determined for these three configurations. Extremely large ratios a _4d ¹⁰/a _4d ⁰¹ were found. Theoretical predictions for the hyperfine structure constants A and B for all levels of the configurations 4d^45s, 4d ⁴5s ² and 4d⁵ have been determined from experimental data. Additionally, the fine and hyperfine structure for the two energetically high lying even configurations 4d^46s and 4d^35s6s are discussed. The results presented here call into doubt the existence of the fine structure levels 4d ³5s6s ⁶ F _11/2 at an energy of 39 408.88 cm^-1 and 4d ³5s5p ⁶ G _13/2 at 18 876.46 cm^-1 given in the Moore tables.     

The electron affinity of tungsten

The electron affinity of tungsten has been measured using laser photodetachment threshold spectroscopy in a collinear geometry. The electron affinity was determined to 6583.6(6) cm^-1 by observing the onset of the process when W^- ions in the 5d⁵6s²5d^56s^2 ⁶S_5/2 ground state are photodetached producing neutral W atoms in the 5d⁴6s²5d^46s^2 ⁵D₀ ground state. The measured value is in agreement with previous measurements and improves the accuracy by almost two orders of magnitude. Further, a photodetachment signal below the ground state photodetachment threshold was found, which indicates the existence of a bound excited state in W^-.     

3391 and 7699 laser generations and questions on the chaos

Summary In this report investigations are presented of laser generations at 3391 nm and 3391 and 7699 nm, or rather of changes induced by them in populations of the 5s′ [1/2] ₁ ⁰ , 4p′[3/2]₂ and 3d′[5/2] ₃ ⁰ levels, depending upon the angle of the tilted mirror of the He−Ne laser system. This writer has discovered that the above laser generations develop at a strongly tilted mirror, when the beam reflected from one mirror, in order to reach the other, has to be reflected many times on the inside walls of the discharge tube. The work was supported by CPBR 8.14.     

高离化态类镍离子电子碰撞激发过程的相对论扭曲波理论研究

利用相对论扭曲波方法和新发展的研究电子碰撞激发过程的计算程序REIE06,系统计算了电子碰撞激发高离化态类镍Gd³⁶⁺和Rn⁵⁸⁺—U⁶⁴⁺(Z=86—92)离子从基态到4l(l=s,p,d,f)次壳层精细结构能级的碰撞强度和截面.研究了随等电子系列变化时,从基态到与X射线激光有关的3d⁹4p和3d⁹4d激发态能级的电子碰撞激发截面随Z的变化,讨论了强的组态相互作用对高离化态类镍离子截面的影响.通过对Gd³⁶⁺离子涉及X射线激光跃迁的相关能级电子碰撞激发速率系数的计算,分析了等离子体中电子温度对碰撞过程的影响.同时,目前部分计算结果与以往的理论结果进行了比较,得到了很好的一致性. 关键词： 电子碰撞激发 相对论扭曲波方法 高离化态类镍离子     

Characterization of collisionally pumped optical-field-ionization soft X-ray lasers

We give an overview of recent experimental results on optical-field-ionization collisional soft X-ray lasers developed at LOA. By focusing a 30-fs, circularly polarized Ti-sapphire laser pulse at an intensity of up to 8×10¹⁷ Wcm^-2 into a low-density gas cell containing Xe or Kr, we produced a few mm long plasma column for soft X-ray amplifier. Saturated amplification has been achieved on the 4d⁹5d(¹S₀)–4d⁹5p(¹P₁) transition at 41.8 nm in Xe⁸⁺, and on the 3d⁹4d(¹S₀)–3d⁹4p(¹P₁) transition in Kr⁸⁺ at 32.8 nm. Under optimum pumping conditions the Xe⁸⁺ laser provides about (5±2)×10⁹ photons per pulse whilst the Kr⁸⁺ laser delivers up to (2.5±1)×10⁹ photons per shot. The repetition rate of these soft X-ray lasers is 10 Hz. The beam wavefront of the Xe⁸⁺ laser has been measured by a Shack–Hartmann soft X-ray wavefront sensor, and the pulse duration by a cross-correlation technique. PACS 42.55.Vc; 32.30.Rj; 52.50.Jm     

Determination of the 5d6p 3F4-5d2 3F transition probabilities of Ba I

Whether the transitions between 6s5d ³D and 5d6p ³F can be used for laser cooling of barium heavily depends upon the transition probabilities of 5d6p ³F-5d^{2 3}F. Taking the transition 6s5d ³D₃-5d6p ³F⁴ as a scale, the leakage rate of 5d6p ³F₄-5d^{2 3}F was used to evaluate the transition probabilities. 706 nm laser pulses with different durations were applied to a barium atomic beam for 6s5d ³D₃-5d^{2 3}F₄ optical pumping, and the remaining percentages in 6s5d ³D₃ were measured. After exponential fitting, the transition probability of 5d6p ³F₄-5d^{2 3}F_3,4 was determined to be 2.1(4)×10⁴ s^?1, which is in agreement with theoretical calculations using the scaled Thomas-Fermi-Dirac method.     

Temporal coherent control induced by wave packet interferences in one and two photon atomic transitions

The interaction of a sequence of two identical ultrashort laser pulses with an atomic system results in quantum interferences as in Ramsey fringes experiments. These interferences allow achievement of temporal coherent control of the excitation probability. We present the results of a temporal coherent control experiment on two different atomic systems: one-photon absorption in K (4s-4p) and two-photon absorption in Cs (6s-7d). In K, the quantum interferences between the two excitation paths associated with the laser pulses are revealed through rapid oscillations of the excitation probability as a function of the time delay between the two pulses. These oscillations take place at the transition frequency (period T = 2.56 fs). The interferences are modulated by beats (at about 580 fs) resulting from the doublet structure of the excited state (4p (² P _1/2 , ² P _3/2 )). Three complementary interpretations of this experiment are presented: in terms of beats of quantum interferences, of variation in the spectrum intensity, and of wave packet interferences. Whenever the two laser pulses are temporally overlapped, optical interferences are superimposed on to the quantum interferences. The distinction between these two types of interference is clearly revealed in the two-photon excitation scheme performed on Cs (6s-7d (² D _3/2 , ² D _5/2 )) because quantum interferences occur at twice the frequency of the optical interferences. Received: 30 December 1997 / Revised: 28 February 1998 / Accepted: 4 March 1998     

Molecular dissociative sequential excitation and ionization of strontium vapor

We report new measurements on laser-assisted molecular dissociative sequential excitation and ionization spectra of strontium vapor. A single Nd:YAG pumped dye laser in conjunction with an atomic beam apparatus have been used to investigate the even parity 5snd ^3,1 D ₂ Rydberg series resulting from the 5s5p ¹ P ₁ resonance level. The relative intensities changes among the 5snd ³ D ₂ and ¹ D ₂ Rydberg series are attributed to the interactions with the 4d6s ^1,3 D ₂ perturbers, respectively. The interchannel interactions between the 5snd ¹ D ₂ series and the 4d6s ¹ D ₂ level and among the 5snd ³ D _1,2,3 series and the 4d6s ³ D _1,2,3 intruders have been separately parameterized using the two-channel quantum defect theory. Received: 10 September 1998 / Received in final form: 16 December 1998     

A narrow linewidth and frequency-stable probe laser source for the <Superscript>88</Superscript>Sr<Superscript>+</Superscript> single ion optical frequency standard

In this paper, we describe in detail a narrow linewidth and frequency-stable laser source used to probe the 5s ² S _1/2–4d ² D _5/2 clock transition of the ⁸⁸Sr⁺ optical frequency standard. The performance of the laser system is investigated with studies of its frequency drift rates and with high resolution spectra of the ⁸⁸Sr⁺ clock transition. The observed short-term drift rates are typically in the range of 10 to 23 mHz/s, and the current long-term drift rate is 13.9(3) mHz/s. The laser stability, after subtraction of linear drifts, reaches 5×10⁻¹⁶ at an averaging time of 3000 s. This high level of stability is attributed for the most part to stabilization of the reference cavity at the temperature where the coefficient of linear thermal expansion crosses zero. An upper bound for the laser linewidth is given by the observation of a Fourier-transform limited resonance of 4.3 Hz (Δν/ν=1×10⁻¹⁴) on the ⁸⁸Sr⁺ clock transition. The effective averaging time during the linewidth measurements was about 100 s.     

Lifetime measurements in Tm I,Tm II,and Tm III by time-resolved laser spectroscopy

Natural radiative lifetimes of eight levels in Tm I ( 4f ¹³5d6p and 4f ¹²5d6s ² configurations), two levels in Tm II ( 4f ¹²5d6s configuration) and three levels in Tm III (4f ¹²5d configuration) have been measured by using time-resolved laser spectroscopy. Free thulium atoms, as well as singly and doubly ionized ions, were obtained in a laser-induced thulium plasma and the investigated states were selectively populated by a single-step excitation process with a tunable narrow-band laser pulse. Received 20 August 2002 / Received in final form 7 January 2003 Published online 4 March 2003 RID="a" ID="a"e-mail: huailiang.xu@fysik.lth.se     

All solid-state continuous-wave intracavity frequency-doubled Nd:LuVO<Subscript>4</Subscript>-LBO red laser at 671.5 nm

We report for the first time a efficient compact red laser at 671.5 nm generation by intracavity frequency doubling of a continuous wave laser operation of a diode direct pumped Nd:LuVO₄ laser on the ⁴ F _3/2 → ⁴ I _13/2 transition at 1343 nm. An LBO crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an absorbed pump power of 16.2 W, as high as 4.3 W of continuous wave output power at 671.5 nm is achieved with 10-mm-long LBO. Comparative results obtained for the pump with diode laser at 808 nm, into the highly-absorbing ⁴ F _5/2 level, are given in order to prove the advantages of the 880 nm wavelength pumping.     

Multimode saturation resonances in optogalvanic spectroscopy: Application to the determination of lande g-factors in zirconium

Resonances corresponding to the matching of laser mode intervals with Lapmor precessional frequencies have been oberved in the discharge current for four transitions in the spectrum of atomic Zr, introduced into a gas discharge by cathodic sputtering. Signals were observed for lower as well as for upper levels. The measured g-factors for the states 4d²5s(a⁴F)5p ³F_2,3,4 and 4d²5s(a²P)5P ³P₂ are symmetrically higher than values given in the literature.     

SrI 4dnp和4dnf奇宇称J=1系列自电离态光谱

用激光三步激发方法,以4d^{2 3}P₀价态为中间态,观察了Sr原子4dnp和4dnf奇宇称J=1系列自电离态光谱,在59570—60300cm^-1范围内,测定了60个自电离能级,其中大多数可归属于分别收敛于4d²D_3/2和4d²D_5/2电离限的6个自电离系列,讨论了光谱线的线型和组态相互作用。 关键词：     

Radiative lifetimes in Ce I and Ce II

New radiative lifetime measurements based on time-resolved laser-induced fluorescence techniques are reported for 18 even-parity levels belonging to the 4f5d^26p and 4f ²5d ² configurations of Ce I and 6 even-parity levels belonging to the 5d^26s, 4f5d6p, and 4f6s6p configurations of Ce II. Free neutral and singly ionized cerium atoms were produced by laser ablation. The Ce I and Ce II levels range in energy from 26 545 to 29 102 cm^-1, and 42 573 to 48 152 cm^-1, respectively. Received 25 September 2002 Published online 4 March 2003     

The Field-Dependent Magnetization of d5–d7 Metal β−Diketonate Complexes and Their Macromolecular Polymers

A vibrating sample magnetometer (VSM) has been used to study the field-dependent magnetization, M(H), of the d⁵?d⁷ metal acetates [M(OAc)₂.nH₂O], metal β?diketonate complexes [M(tba)₂(H₂O)₂] and the macromolecular polymers [M(tba)₂(4,4-bipy)]_n (where, M = Mn(II), Fe(II), and Co(II), OAc = O₂CCH₃, tba = deprotonated 3-benzoyl-1.1.1-trifluoroacetone, and 4,4-bipy = 4,4′-bipyridine). The magnetic field strength (H) was applied in the range of 0?10⁴ O_e at ambient temperature (ca. 23°C). The experimental results showed that the d⁵?d⁷ metal acetate, complexes and polymers exhibit low paramagnetic properties excepting [Fe(tba)₂(4,4-bipy)]_n polymer, which had negative magnetization M(emu/g) showing diamagnetic properties in the range 0?10⁴ O_e. The magnetization was almost equal to zero without an applied magnetic field (H(O_e)) for each d⁵?d⁷ metal acetate, complex, and polymer. The linear M(H) curve had a magnetic saturation for iron and manganese acetate species at the magnetic field strengths of 3.1 × 10³ and 4.7 × 10³ Oe, respectively. The external magnetic field reached 9.0 × 10³ O_e without any saturation magnetization for the cobalt compounds. The coordination effect of 3-benzoyl-1.1.1-trifluoroacetone (H-tba) and 4,4′-bipyridine (4,4′-bipy) ligands on the field-dependent magnetization M(H) and paramagnetic behavior of d⁵?d⁷ metal atoms is discussed. The field-dependent magnetization M(H) curves of metal β?diketonate complexes and the polymers including d⁵?d⁷ metal acetates showed a weak field octahedral geometry.     

OPTICAL ISOTOPE SHIFTS OF Nd II (25524)011/2 USING COLLINEARFAST-ION-BEAM LASER SPECTROSCOPY

Fast-ion-beam laser spectroscopy which has the characteristics of selective excitation and high accurate measurement was widely used to study isotope shifts, radioactive lifetimes, and hyperfine structures of atoms and ions. In this work, the optical isotope shifts for the transition 4f⁴5d⁶K_13/2-(25524)⁰_13/2 in Nd II were measured by using collinear fast-ion-beam lase r spectroscopy.     

Sub-doppler laser cooling of thulium atoms in a magneto-optical trap

Sub-Doppler laser cooling in a magneto-optical trap for thulium atoms at a wavelength of 410.6 nm has been experimentally studied. Without any dedicated molasses period of sub-Doppler cooling, the cloud of 3 × 10⁶ atoms at a temperature of 25(5) μK was observed. The measured temperature is significantly lower than the Doppler limit of 240 μK for the cooling transition at 410.6 nm. The high efficiency of the sub-Doppler cooling process is due to a near-degeneracy of the Landé g-factors of the lower 4f ¹³6s ² (J = 7/2) and the upper 4f ¹²5d _3/26s ² (J = 9/2) cooling levels.     

Determination of hyperfine structures and Rydberg convergence limits of selected optical transitions in 93Nb using resonance ionization spectroscopy

Several two- and three-step schemes for resonance ionization of ⁹³Nb with field ionization of Rydberg levels were investigated in the context of feasibility studies of using ^93m Nb/⁹³Nb isomer ratio determination for fast neutron dosimetry. Hyperfine structures of the states 4d ⁴(a ⁵ D)5p ⁴ D ₁ ^2/0 , 4d ³5_s(a ⁵ P)5P ⁶ D ₁ ^2/0 , 4d ³5s(a ⁵ F)5p ⁶ F ₁ ^2/0 , and 4d ³5s(a ⁵ F)6s ⁶ F _1/2 of ⁹³Nb were measured. The Rydberg spectra of the excitation schemes were measured and corresponding ionization limits estimated.     

Energieverlust und Lichtausbeute bei axialem Channeling von α-Teilchen in Anthrazen

In an atomic beam experiment we measured the hyperfine structure (hfs) of the metastable states 3d ² 4s ⁴ F _3/2,9/2 of Scandium, which were populated by electron impact. A single mode cw dye laser was used to create a population difference between neighbouring hfs states by optical pumping. Rf transitions between these states, equalizing the population numbers, could then be detected by repeating the optical pumping experiment and looking for the laser induced fluorescent light. The following constants of the magnetic dipole and electric quadrupole interactions have been obtained by this method:A _3/2=–158.513(3)MHzB _3/2=–5.19(2)MHzA _9/2=285.967(9)MHzB _9/2=–15.46(70)MHzFrom these constants and the corresponding values forJ=5/2, 7/2, as measured by [1], the following parameters can be calculated: r ^–3 _d ⁰¹ =0.911(4)a ₀ ^–3 r ^–3 _d ¹² =2.395 (62)a ₀ ^–3 and:=r ^–3 _d ⁰¹ /r ^–3 _d ¹² =0.38(1).     

Resonant inelastic x‐ray scattering from highly correlated dysprosium compounds

Dy₂O₃ and Dy metal's resonant inelastic x‐ray scattering (RIXS) spectra were measured in the Beijing Synchrotron Radiation Facility. As a bulk sensitive probe and two‐photon process, RIXS provides more information on the electronic structure of matter. In this full RIXS experiment, the 2p⁶4fⁿ→ 2p⁵4fⁿ5d¹ (2p⁵4f^{n + 1}5d⁰) → 2p⁶3d⁹4fⁿ5d¹ (2p⁶3d⁹4f^{n + 1}5d⁰) channel of two samples (Dy₂O₃ and Dy metal) was studied. Further comparison shows that there are many differences in the RIXS spectra. Dy metal has only a single resonance and its 5d band is broader than that of Dy₂O₃. In the resonant regime, it has a lower final state energy, whereas in the non‐resonant regime it exceeds Dy₂O₃. This causes a broader bandwidth of the main final state B and a narrower bandwidth in the resonant and non‐resonant regime. The pre‐edge structure in Dy L₃ absorption spectra was also resolved using RIXS, which cannot be seen in conventional XAS owing to 2p core hole lifetime broadening. Copyright © 2005 John Wiley & Sons, Ltd.