First observation of a resonance ionization signal on242mAm fission isomers

The feasibility of a hyperfine spectroscopy on^242mAm fission isomers has been demonstrated at the low target production rate of 10/s. The experimental method employed is based on resonance ionization spectroscopy in a buffer gas cell with detection of the ionization process by means of the fission decay of the isomers. The resonance ionization has been performed in two steps, utilizing an excimer dye laser combination with a repetition rate of 300 Hz. The first resonant step proceeds through theJ=7/2 term at 21440.35 cm⁻¹, which has been excited with the tuncable dye laser beam of a wavelength of 466.28 nm, the second non-resonant step is achieved with the 351 nm radiation of the excimer laser itself, running with XeF. The frequency scan of the tuneable dye laser exhibits a broad resonance ionization signal, the width of which is most likely explained by the magnetic hyperfine interaction.     

Optical pumping for investigation of nuclear properties of short-lived isotopes/isomers: A review

Optical Pumping (OP) is an efficient technique to produce oriented nuclei by absorption of polarized light by atoms. With the advent of tunable lasers, both resolution and sensitivity of the OP technique has greatly increased. The optically induced nuclear orientation produces changes in the angular distribution of nuclear emissions. The β-asymmetry or γ-anisotropy of the optically oriented nuclei is frequency dependent and the hyperfine structure of short-lived isotopes/isomers may be studied by monitoring the asymmetry/anisotropy as a function of laser tuning. This brief review describes the recent developments in the OP technique for studying the short-lived isotopes/isomers and lists all the nuclei studied so far by this technique.     

Resonance photoionization spectroscopy and laser separation of 141Sm and 164Tm nuclear isomers

The 141g and 141m samarium and 164g and 164m thulium nuclear isomers have been separated for the first time by the laser selective atomic photoionization technique in on-line experiments with a proton accelerator and a mass separator. The hyperfine structure of the ¹⁴¹Sm isomer lines has been studied and the nuclear parameters μ, Q, and δ 〈r²〉 of the isomers determined.     

New laser setup at the IRIS facility. Magnetic moments and mean squared charge radii of neutron deficient Tl isotopes

A new laser installation for the resonance ionization spectroscopy in a laser ion source and for rare isotope production has been put into operation at the IRIS mass-separator, working on-line with the 1 GeV proton beam of the Petersburg Nuclear Physics Institute synchrocyclotron. Isotope shift and hyperfine splitting of 276.9 nm atomic transition in the long chain of Tl isotopes and isomers have been measured. New data on the magnetic moments and changes in mean squared charge radius for ^{183,184,185,185m,186m2,195m,197m}Tl have been obtained.     

铯原子7S1/2态磁偶极超精细常数的测量

在室温下的原子气室中, 基于铯原子6S_1/2-6P_3/2-7S_1/2(852.3 nm+1469.9 nm) 阶梯型能级系统, 利用电光调制器的主频和±1级边带分别产生的三套双共振吸收光谱, 当驱动电光调制器的信号源频率严格等于7S_1/2态超精细分裂的能级间隔时, 三套谱线中的一些超精细跃迁谱线重叠且线宽最窄, 利用这一现象很好地避免了激光器频率扫描时非线性效应的影响, 测量出了7S_1/2 态超精细分裂能级间隔: 2183.72 MHz±0.23 MHz, 并计算出该态的磁偶极超精细常数: A_hfs= 545.93 m MHz±0.06 MHz, 与文献中报道的测量结果一致.     

Frequency measurements in the 9μm spectrum of CF3Br

Carbon dioxide laser saturation spectra of CF₃ Br have been explored with a view to hyperfine spectroscopy and references for frequency standards in the 9μm band of the carbon dioxide laser. Spectra have been obtained using the laser transitions 9R(16)-9R(30). and show many saturation features in each case. Several of the stronger features have been referenced directly to CO₂ frequencies with an estimated accuracy of 25 kHz. Spacings between the hyperfine components are also reported. This work represents some of the first data relevant to 9μm locking to molecular absorptions.     

Optical pumping and population transfer of nuclear-spin states of caesium atoms in high magnetic fields

Nuclear-spin states of gaseous-state Cs atoms in the ground state are optically manipulated using a Ti:sapphire laser in a magnetic field of 1.516T, in which optical coupling of the nuclear-spin states is achieved through hyperfine interactions between electrons and nuclei. The steady-state population distribution in the hyperfine Zeeman sublevels of the ground state is detected by using a tunable diode laser. Furthermore, the state population transfer among the hyperfine Zeeman sublevels, which results from the collision-induced modification \delta a(\bm S \cdot \bm I) of the hyperfine interaction of Cs in the ground state due to stochastic collisions between Cs atoms and buffer-gas molecules, is studied at different buffer-gas pressures. The experimental results show that high-field optical pumping and the small change \delta a(\bm S \cdot \bm I) of the hyperfine interaction can strongly cause the state population transfer and spin-state interchange among the hyperfine Zeeman sublevels. The calculated results maybe explain the steady-state population in hyperfine Zeeman sublevels in terms of rates of optical-pumping, electron-spin flip, nuclear spin flip, and electron-nuclear spin flip-flop transitions among the hyperfine Zeeman sublevels of the ground state of Cs atoms. This method may be applied to the nuclear-spin-based solid-state quantum computation.     

Explanation for the effect of natural strong narrowing of Mössbauer lines on long-lived isomers. Variety of nuclei and media with this effect

The effect of natural strong narrowing (NSN) of Mössbauer lines on long-lived isomers has been explained. This effect was doubted for more than thirty years because its mechanism was unknown. The mechanism of NSN has been revealed. Its threshold condition has been established. The theory of inhomogeneous broad-ening of a line in the case of NSN has been developed. Broadenings owing to magnetic, quadrupole, and 2 ^L -pole hyperfine interactions are suppressed almost to zero at NSN. The mechanism of NSN provides a width about the natural width. The linewidth at NSN is independent of the magnitude and direction of the magnetic field if it is lower than ～100 G. The variety of nuclei and media with NSN or with the collapse of the hyperfine interaction (responsible for NSN) is outlined.     

窄带激光与能级具有超精细结构的二能级原子的相干激发

将原子相干激发动力学的半经典理论拓展到了有超精细分裂能级 的情形，并对具体原子能级进行了计算. 研究结果表明，当激光功率达到一定水平后，由于 功率加宽的作用，单频激光也能将有超精细分裂能级的原子有效地激发. 因此，在这样激光 功率条件下，为提高原子激发效率而增加激光谱线宽度的做法并不是必要的. 关键词： 超精细结构 二能级原子 Rabi频率 钆原子     

Selection of oscillation frequency in the 1.315 μm iodine laser

Tuning of an iodine oscillator at 1.315 μm has been carried out with an in-cavity, temperature controlled solid etalon; the hyperfine transition detail and pressure shifts have been observed. This enables the hyperfine transition and the laser frequency of an oscillator-amplifier system to be selected for use in pulse propagation studies or high power laser applications.     

Velocity selective optical pumping and repumping effects with counter and copropagating laser radiations for D<Subscript>2</Subscript> lines of rubidium

The effects of a strong control or pump laser, counter propagating or copropagating with the probe beam, on the probe absorption spectra of ⁸⁵Rb and ⁸⁷Rb-D₂ transitions have been investigated inside a room temperature Rb vapour cell. In both cases a set of strong velocity selective resonance dips are observed at different velocities. Their movements across the Doppler broadened probe absorption profile have been studied for different lock frequencies of the control laser. These spectra are modified by optical pumping effects due to the presence of another hyperfine component of the ground state. A repumping laser, from the dark hyperfine component of the ground level transfers almost 75% of the atoms from the dark state to the pump probe cycle hence reducing the optical pumping effect. A numerical simulation is done to explain the observed spectra. The effect of a control laser on the Lamb dip spectrum of the probe laser has also been investigated. The control beam is used to improve the strength of a weak hyperfine dip on the Doppler broadened probe spectrum. The strength of the hyperfine dip increases by a factor of 3.2 in presence of the control laser. The observed dips show that pump-probe spectroscopy can be used as velocity selectors of atoms.     

Radiation detected resonance ionization spectroscopy on208Tl and242fAm

An ultra-sensitive laser spectroscopic method has been developed for the hyperfine spectroscopy of short-lived isotopes far off stability produced by heavy ion induced nuclear reactions at very weak intensity (> 1/s). It is based on resonance ionization spectroscopy in a buffer gas cell with radiation detection of the ionization process (RADRIS). As a first on-line application of RADRIS optical spectroscopy at^242fAm fission isomers is in progress at the low target production rate of 10/s. The resonance ionization has been performed in two steps utilizing an excimer dye laser combination with a repetition rate of 300 Hz. The first resonant step proceeds through terms which correspond to wavelengths of 466.28, 468.17 or 426.56 nm; the second non-resonant step is achieved with the 351 nm radiation of the excimer laser itself, running with XeF. The frequency scans of the tuneable dye laser at 466.28 and 468.17 nm exhibit broad resonance ionization signals, the latter with a large isotope shift between^242fAm and²⁴³Am which is in accordance with the large quadrupole moment of the^242fAm fission isomer.Work supported by the Bundesministerium für Forschung und Technologie under contract 06 MZ 188 I.     

Two-photon Fourier spectroscopy with femtosecond light pulses

We demonstrate a Fourier spectrometer that uses intense ultrashort laser pulses. By exciting the 6S(1/2) - 8S(1/2) two-photon transition in atomic cesium vapor, we are able to measure the small hyperfine splitting of the 8S(1/2) excited state. This technique, combining a high spectral resolution with the high peak intensities available to femtosecond laser systems, may offer intriguing opportunities for the study of multiphoton transitions and for spectroscopy in the short-wavelength region.     

Sub-Doppler laser absorption spectroscopy of the AΠi − XΣ (1, 0) band of CN: Measurement of the N hyperfine parameters in AΠ CN

Measurements of multiple rotational lines in the (1, 0) band of the A²Π_i − X²Σ⁺ “red” system of the cyanogen radical (CN) at sub-Doppler resolution are reported. The CN radical was produced by 193 nm photodissociation of NCCN (ethane dinitrile) and detected with a Ti:sapphire ring laser operating near 10 900 cm⁻¹. The sample was exposed to a weak, frequency-modulated probe beam and a strong, counterpropagating bleach laser beam. Demodulated probe laser signals display absorption and dispersion features derived from Doppler-free saturation of the hyperfine components as the laser scans across the central region of a Doppler-broadened rotational line spectrum. Hyperfine-resolved transition frequencies were combined with known ground-state X²Σ hyperfine term values to determine A²Π state hyperfine term values, which were analyzed in terms of an effective Hamiltonian for the A²Π state. All the expected hyperfine and ¹⁴N quadrupolar parameters were determined and their values analyzed in terms of a simple molecular orbital picture of the bonding in the radical. Higher sensitivity obtained with 400 kHz amplitude modulation of the bleach laser and additional phase-sensitive detection allowed hyperfine splittings in some rotational lines of ¹³C¹⁴N to be observed in natural abundance. Excited state hyperfine splittings were determined for a selection of rotational states, but not enough to determine the ¹³C hyperfine parameters.     

Charge radii and moments of strontium nuclei by laser spectroscopy

The isotope shifts and hyperfine splittings for 11 strontium isotopes (A=80–90) and two isomers for the optical transition λ=293.2 nm were measured. The magnetic dipole and electric quadrupole moments and the changes of the mean square charge radii are derived. The results are discussed with respect to the increasing nuclear deformation and the anomalous coupling scheme of light Sr nuclei.     

Observation of the nuclear magnetic octupole moment of 133Cs

We describe our high-resolution measurements of the 133Cs 6p (2)P(3/2) state hyperfine structure. An optically narrowed diode laser excites perpendicularly a highly collimated atomic beam. The spectra are calibrated with a stable reference diode laser using a rf locking scheme allowing us to determine the splittings with an accuracy of < or =2 kHz, an order of magnitude better than previous results. The magnetic dipole a, electric quadrupole b, and magnetic octupole c hyperfine coupling constants are determined. The values we obtained are a=50.288 27(23) MHz, b=-0.4934(17) MHz, and c=0.56(7) kHz. This work represents the first observation of the magnetic octupole moment of the cesium nucleus. We carry out atomic-structure calculations and determine the nuclear electric quadrupole moment Q= -3.55(4) mb and nuclear magnetic octupole moment Omega=0.82(10) b x mu(N).     

基于超精细结构下的激光光泵铯磁力仪的理论研究

激光光泵碱金属磁力仪具有很高的灵敏度,测量范围可以从地球磁场到生物磁场。给出了铯（Cs）光泵磁力仪的理论分析和系统设计以及磁场梯度测量原理,铯原子能级在I—J耦合时形成超精细结构,在外磁场的作用下超精细结构进一步产生塞曼分裂形成塞曼子能级,利用激光泵浦和射频磁场能够使电子在超精细结构中进行能级跃迁,产生光磁双共振的结果,最终通过共振频率就能够达到精确测量外磁场的目的。     

Laser probing of ions in a storage ring: A method for selective determination of lifetimes of metastable states

A collinear laser probing technique is introduced for use in ion storage rings. This method can be used for high resolution studies of the decay properties of metastable states in ions. An experiment on singly charged xenon utilizing this technique is presented. By selective excitation of individual hyperfine states a drastic hyperfine induced quenching was observed. Systematic effects from ion beam neutralization in the rest gas and mixing effects occurring in the bending magnets are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

On the hyperfine spectral lines of an atomic copper vapor laser

The hyperfine structure of energy levels of copper atom and its transition probabilities were considered. The resonance and metastable levels of the copper atom are split into hyperfine structures, due to the magnetic dipole moment and the electric quadrupole moment. In this paper, a succinct introduction to the relevant theory of the hyperfine spectral structure and experimental observations of elemental copper vapor laser is presented.