Isotope shifts and hyperfine structure of erbium,dysprosium, and gadolinium by atomic-beam diode-laser spectroscopy

A commercial diode laser system, without external frequency stabilization, has been used to study the isotope shifts and hyperfine structure in a near infrared transition of erbium, dysprosium and gadolinium. Specific mass shifts and relative values for the change in the radial nuclear charge parameters of the isotopes were obtained for erbium and dysprosium that compare well with literature values. The hyperfine structure constants measured for erbium fell within the range predicted from the results of other workers. The isotope shifts in the gadolinium transition investigated were too small for the spectrum to be resolved.     

Magnetic hyperfine fields of Nb andMo in nickel by NMR-ON of90Nb and93mMo

The magnetic hyperfine splitting frequencies of⁹⁰NbNi and^93mMoNi in an external magnetic field of 0.2 T have been determined by the NMR-ON method to be 18.52(7) and23.73(10) MHz, respectively. With the assumption of Knight shift factorK=0 and with the knowng-factors, the hyperfine fields of⁹⁰NbNi and^93mMoNi were deduced asB _HF(⁹⁰NbNi)=-4.118(16) T andB _HF(^93mMoNi)=-3.491(33) T. The rather long spin-lattice relaxation time of 32(5) min was observed for⁹⁰NbNi at an external magnetic field of 0.2T and8 mK.     

Contactless electroreflectance spectroscopy of optical transitions in low dimensional semiconductor structures

The authors present the application of contactless electroreflectance (CER) spectroscopy to study optical transitions in low dimensional semiconductor structures including quantum wells (QWs), step-like QWs, quantum dots (QDs), quantum dashes (QDashes), QDs and QDashes embedded in a QW, and QDashes coupled with a QW. For QWs optical transitions between the ground and excited states as well as optical transitions in QW barriers and step-like barriers have been clearly observed in CER spectra. Energies of these transitions have been compared with theoretical calculations and in this way the band structure has been determined for the investigated QWs. For QD and QDash structures optical transitions in QDs and QDashes as well as optical transitions in the wetting layer have been identified. For QDs and QDashes surrounded by a QW, in addition to energies of QD and QDash transitions, energies of optical transitions in the surrounded QW have been measured and the band structure has been determined for the surrounded QW. Finally some differences, which can be observed in CER and photo-reflectance spectra, have been presented and discussed for selected QW and QD structures.     

Determination of90Sr in environmental samples with resonance ionization spectroscopy in collinear geometry

A new, fast technique for trace analysis of the radioactive isotopes⁸⁹Sr and⁹⁰Sr in environmental samples has been developed. Conventional mass separation is combined with resonance ionization spectroscopy in collinear geometry, which provides high selectivity and sensitivity. In addition, a chemical separation procedure for sample preparation has been developed. The described technique was used to determine the⁹⁰Sr content in 870 m³ air samples collected near Munich during and shortly after the Chernobyl reactor accident in April 1986. The content of⁹⁰Sr was measured to be 1.4 mBq per m³, corresponding to 1.6 × 10⁹ atoms of⁹⁰Sr per sample. This value is in good agreement with the results of radiochemical measurements.This publication comprises part of the Dissertations of J. Stenner and K. Zimmer     

Determination of phase transitions in binary systems of mesogenic compounds by optical absorption spectroscopy

The use is described of absorption spectroscopy for determining phase transitions in the mesogenic compound cholesteryl myristate (CM) and in binary mixtures of terephthalbis-butyl-aniline (TBBA) and cholesteryl myristate. The temperature dependence of the optical densities in the visible region at phase transitions is reported. The transition temperatures obtained with this method are in good agreement with the results obtained with other methods.     

Ordered structures and statistical properties of ion clouds stored in a Paul trap

A numerical investigation of the dynamics of ions forming small clouds confined in a Paul trap has been performed by means of a Monte-Carlo simulation. Inclusion of laser cooling results in crystallization of the trapped ions. The shape of ordered structures is predicted.     

Nonlinear optical spectroscopy of electronic transitions in hexagonal manganites

The hexagonal rare-earth manganites RMnO₃ (R = Sc, Y, Ho, Er, Tm, Yb, Lu) are a group of materials with an unusual combination of magnetic, electric and optical properties. The electronic structure of these materials was studied by second harmonic (SH) spectroscopy in the range from 1.2 to 3.0 eV. Faraday rotation and absorption spectra were measured in the range from 1.0 to 1.6 eV. Broad bands at ∼1.7 eV and ∼2.7 eV are assigned to electronic transitions between Mn³⁺(3d⁴) levels. The SH spectra are discussed on the basis of a recently developed microscopic theory. Received: 26 April 2001 / Published online: 18 July 2001     

Doppler-free optical double resonance spectroscopy using a single-frequency laser and modulation sidebands

Principles and applications are described for a form of Doppler-free optical double resonance spectroscopy which uses amplitude modulation sidebands (v _L ±v) imposed on a single laser frequency (v _L ). The sidebands are generated by passing the carrier radiationv _L through an electro-optic modulator, driven at a radiofrequency ν, which enables the intensity and polarization characteristics of the emerging radiation to be varied for enhancement of selected double-resonance processes. The technique has been applied to infrared-infrared double-resonance studies of the Stark effects of a variety of molecules—¹³CH₃F,¹²CH₃F, PH₃,¹⁵NH₃, GeH₄, SiH₄, and CH₃D—for which physical results are presented and discussed. These results include determination of extremely small electric dipole moments (10⁻³–10⁻⁵ debye) for GeH₄ and CH₃D and, for the dipole moment of PH₃, a vibrational state dependence which is extremely small (Δμ=0.0028(5) debye for ∣Δv ₂∣=1) and a rotational state dependence which is of an unexpected sign. The spectra recorded in some cases display unusual polarization and optical saturation effects which deviate markedly from the predictions of a simple three-wave polarization theory.     

邻羟基苯腈的双色共振增强多光子电离光谱及Franck-Condon模拟

在自制直线式飞行时间质谱仪上进行了双色共振增强双光子电离实验,获得了振动分辨的邻羟基苯腈的共振增强多光子电离(resonance enhanced multiphoton ionization, REMPI)光谱,结合高精度密度泛函理论计算和Franck-Condon光谱模拟,详细分析了光谱特征,发现了大量基频、泛频和组合振动,并进行了光谱归属.大部分苯环的基频振动归属为环在平面内的畸变或平面内的摇摆,这与分子激发过程中苯环的扩张有关.理论和实验结果都表明, REMPI光谱的低频段信号强,背景低,谱带少,分辨率好.随着振动频率的增加,信号向相反的方向变化.这是由于低频段光谱主要来自于低频的基频振动、少量泛频的贡献.随着振动频率增加,泛频和各种模的组合振动逐渐增多,导致了高频区谱带稠密,分辨率变差.高阶振动和多模的组合振动通常有较低的Franck-Condon因子,因此信号随频率增大逐渐变弱,信噪比变差.     

Effective resonance transitions in quantum optical systems: Kinematic and dynamic resonances

We show that quantum optical systems preserving the total number of excitations admit a simple classification of possible resonant transitions (including effective ones), which can be classified by analyzing the free Hamiltonian and the corresponding integrals of motion. Quantum systems not preserving the total number of excitations do not admit such a simple classification, so that an explicit form of the effective Hamiltonian is needed to specify the allowed resonances. The structure of the resonant transitions essentially depends on the algebraic properties of interacting subsystems. Paper submitted by the authors in English on 30 May 2006.     

Theoretical studies of isotope shifts,hyperfine structures and oscillator strengths in transitions between low-lying levels in O I

Multiconfiguration Hartree-Fock (MCHF) and configuration interaction (CI) calculations have been performed for the low-lying levels 2p^{4 3}P, 2p³(⁴S⁰)3s ^3,5S⁰ and 2p³(⁴S⁰)3p ^3,5P⁰ of neutral oxygen. Different cancellation effects on the specific mass shift, on the electronic contributions to hyperfine interaction constants and on the length and velocity forms of oscillator strengths are illustrated. The final CI values are compared with experimental values and, when available, with values from other theories.     

Resonant two-photon ionization and mass-analyzed threshold ionization spectroscopy of the selected rotamers of m-methoxyaniline and o-methoxyaniline

We report the resonant two-photon ionization and mass-analyzed threshold ionization (MATI) spectra of m-methoxyaniline and o-methoxyaniline. The vibronic features of m-methoxyaniline are built on 34308 ± 2 and 34495 ± 2 cm⁻¹ corresponding to the origins of the S₁ ← S₀ electronic transition (E₁’s) of the cis and trans rotamers. Analysis of the MATI spectra gives the adiabatic ionization energies (IEs) of 59983 ± 5 and 60879 ± 5 cm⁻¹ for these two species. o-Methoxyaniline is found to have only one stable structure whose E₁ and IE are 33875 ± 2 and 58678 ± 5 cm⁻¹, respectively. Most of the active vibrations of m- and o-methoxyaniline in the electronically excited S₁ and cationic ground D₀ states result from the in-plane ring vibrations. Comparing these data with those of p-methoxyaniline allows us to learn about the vicinal substitution effects resulting from the relative locations of the NH₂ and OCH₃ substituents.     

H Magnetic resonance imaging and P magnetic resonance spectroscopy in experimental filariasis

¹H Magnetic resonance imaging and ³¹P magnetic resonance spectroscopy (MRS) have been carried out in experimental rodent filariasis, i.e., Acanthocheilonema viteae infection in the rodent host, Mastomys coucha. The T₂-weighted image of the infected host shows fine hyperintense thread like structures of adult filariid nests in the cervical region. ³¹P MRS of normal and infected hosts, localized over the same region of interest, show seven major peaks corresponding to phosphomonoesters (including glucose-6-phosphate, fructose-6-phosphate, fructose-1-6-diphosphate, phosphorylcholine, and adenine monophosphate or AMP), inorganic phosphate, glycerophosphorylcholine, phosphoenolpyruvate, phosphocreatine and nucleoside di- and tri-phosphates. Concentrations of phosphomonoesters (PMEs) are higher in the normal rodent compared with the infected ones. In vivo ³¹P MRS provides a non-invasive assessment of tissue bioenergetics and phospholipid metabolism.     

Optimization and limits of optical nonlinear measurements using imaging technique

We report on analytical calculations for a 4f coherent imaging system in presence of a phase object at the entry of the set-up. We give the results of the optimized parameters to be used in this system so as to increase the sensitivity of the measurement of the nonlinear refraction coefficient. Analytical and previously reported simulated image profiles are compared here. Our study also gives the limits of the nonlinear imaging technique with a phase object for relatively high nonlinear phase shifts.     

Determination of thickness and optical dispersion property of gold film using spectroscopy of surface plasmon in frequency domain

We propose to use wavelength modulation approach, i.e., the spectroscopy of surface plasmon in frequency domain to characterize the optical dispersion property of gold film. Using this method, we determine the dispersion relationship of gold film in a wavelength range from 537.12 nm to 905.52 nm, and our results accord well with the reported results by other authors. This method is particularly suited for studying the optical dispersion properties of thin metal films, because a series of dielectric constants over a wide spectral range can be determined simultaneously via only a single scan of the incident angle, thereby avoiding the repeated measurements required when using angular modulation approach.     

Radio-frequency laser double-resonance spectroscopy of trapped171Yb ions and determination of line shifts of the ground-state hyperfine resonance

The paper reports on radio-frequency laser double-resonance experiments on¹⁷¹Yb ions confined in a cylindrically symmetric electrodynamic trap in the presence of helium buffer gas. The optical-excitation scheme relies on the selective excitation of a cycling hyperfine component of the = 370 nm resonance transition. Additional excitation of a transition at = 935 nm prevents population trapping of ions in the metastable² F _7/2 level. Using a maser reference, the ground-state hyperfine resonance frequency is measured under conditions of a systematic variation of confinement conditions. Kinetic temperatures and the resulting relativistic resonance shifts are inferred from the inhomogeneous broadening of the optical resonance transition. Shifts of the hyperfine resonance frequency due to quadratic Stark effect and collisions are determined. By extrapolation, the unperturbed transition frequency is determined as 12 642 812 118.471 (9) Hz.     

Study of hyperfine interactions in pure and Co-doped CeO2 nanoparticles by PAC spectroscopy using 111Cd

In this work we have used the Perturbed Angular Correlation (PAC) technique to measure the hyperfine interactions in pure nanostructured (crystallite size around 70 nm) as well as doped with 3d transition metal Co (3 at. %) CeO₂ samples. The PAC measurements were performed at different temperatures between 23 and 527°C. The results did not reveal any evidence of hyperfine magnetic interactions. Spectra obtained presented three major frequencies related to substitutional sites in CeO₂, grain boundary sites and intrinsic defect related sites.     

Nuclear moments and the change in the mean square charge radius of neutron deficient thallium isotopes

The hyperfine structure, isotope and isomeric shifts in the atomic transition 6p ² P _3/2–7s ² S _1/2, =535 nm have been measured for theI=7 andI=2 states of^{190, 192, 194, 196}Tl; theI=1/2 andI=9/2 states of¹⁹¹Tl and the I=7 isomer of¹⁸⁸Tl. The thallium isotopes were prepared as fast atomic beams at the GSI on-line mass separator following fusion reactions and — in some cases — subsequent-decay. The nuclear dipole moments, electric quadrupole moments and the change in the nuclear mean square charge radius are evaluated. Theuu-isotopes show an isomeric shift which changes sign between¹⁹²Tl and¹⁹⁴Tl.Dedicated to P. Armbruster on the occasion of his 60th birthday