Submillimeter measurements of isotopes of nitric acid

The ground and low-lying vibrational states of nitric acid are observable with current instrumentation in the Earth’s thermal submillimeter atmospheric emission. Remote sensing continues to improve to higher sensitivity and future missions will allow these measurements with minimal integration time. Sensing of weaker spectral features will require signal averaging, and choices of spectral windows for these features will require knowledge of the higher vibrational states and rare isotopes of the strongly emitting species. Nearly comprehensive information on vibrational states and isotopically substituted species is now available from wide bandwidth scans of natural and isotopically enriched nitric acid. In this work, ground state rotational spectra of five isotopically substituted species of nitric acid are analyzed in the submillimeter spectral range. We present the Hamiltonian parameters necessary for prediction and identification of isotopic features across the nitric acid ground state rotational spectrum.     

Submillimeter BWO spectroscopy of solids

The potentialities of submillimeter spectroscopy (3–30 cm^–1) based on backward wave oscillators for studying solids are discussed. The scope of the research on this problem made at the Institute of General Physics of the USSR Academy of Sciences is outlined.     

Submillimeter spectroscopy of materials with correlated electrons

We describe the techniques which permit one to measure the electrodynamic response of conductive materials in the millimeter and submillimeter wavelength ranges. Results of studying dielectric spectra of a number of materials whose properties are determined by electron correlations, e.g., superconductors, one-dimensional conductors, and compounds with heavy fermions, are presented.     

Laser spectroscopy of the bismuth isotopes

Isotope shifts and hyperfine structures of the bismuth isotope chain have been studied on the 306.7 nm line in off-line measurements using gas cell laser spectroscopy and atomic beam spectroscopy. The changes in nuclear mean square charge radii and the nuclear magnetic and spectroscopic quadrupole moments have been deduced. The neutron-rich isotopes are the first isotones of Pb to be measured immediately above the N=126 shell closure. A remarkable correspondence between the nuclear charge radii of the Bi and Pb isotope chains is demonstrated by a King Plot analysis. The relationship between nuclear shapes and the charge radii can be understood in the framework of the spherical shell model using few-nucleon configurations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Laser spectroscopy of radioactive isotopes

The experimental conditions for laser spectroscopy of shortlived isotopes is discussed with respect to nuclear lifetime, reaction rates and samples preparation by on-line mass-separator techniques. The method of collinear laser spectroscopy is presented with results for medium mass elements near the closed proton shell Z=50. An interpretation of magnetic moments, spectroscopic quadrupole moments and the parabolic shape of the isotope shift in this region of nuclei is given.     

Nuclear spectroscopy of molybdenum isotopes

The dependence of the properties of low-lying states of Mo isotopes on the mass number A = 83–117 is studied based on the collective and shell models of atomic nuclei. The variation of the nuclear shape with an increasing number of neutrons influences strongly the properties of excited states of Mo isotopes. Decay channels of isovector giant dipole resonance with emission of protons and neutrons are studied in the framework of the combined model. The basic mechanisms of the production of stable Mo isotopes in astrophysical nuclear reactions are described.     

Laser spectroscopy of stable Os isotopes

Doppler-free isotope shift measurements of the stable even ^184–192Os and ^187,189Os odd isotopes have been performed for the first time on the 5d ⁶6s ^{2 5}D₄→5d ⁶6s6p ⁷F₄ (305.9 nm) transition in the neutral atom by atomic beam laser spectroscopy and on the ionic 5d ⁶6s ⁵D_9/2→5d ⁶6p ⁶D_7/2 (228.2 nm) transition by fast collinear ion-laser spectroscopy. The measurements were carried out in Manchester and at the IGISOL facility in Jyväskylä in Finland, respectively. The results presented are the most precise measurements to-date of the absolute isotope shifts.     

Reaction spectroscopy with even tin isotopes

The two-particle transfer reactions ^{116, 118}Sn(t, p) and the inelastic scattering of 55 MeV protons from ¹¹⁶Sn and 16 MeV protons from ^{116, 118, 120}Sn are analysed for various transitions to collective and non-collective states in the final nucleus using DWBA. Form factors have been calculated with wave functions containing two-quasiparticle excitations of neutrons in open and closed shells as well as 1p-1h transitions from closed proton shells. In the inelastic scattering, generally a Serber-type Gaussian effective interaction was inserted. The results are compared with those obtained on the assumption of two-quasiparticle excitations in a restricted configuration space only. For both types of reaction, reasonable agreement with experimental data is obtained for the angular distribution. In the (t, p) reaction the measured and calculated relative cross sections agree within a factor of two. For the inelastic scattering, apart from relative cross sections the mass dependence of the collective excitations and the influence of four-quasiparticle excitations have been examined. The transition to the collective 2⁺ level in ¹¹⁶Sn was calculated with the proton component of the wave function corrected according to electromagnetic measurements. From inelastic scattering it follows that the transitions to negative-parity states especially are not described satisfactorily by the wave functions used. Cross sections for unobserved higher excited levels have been estimated.     

High resolution spectroscopy of stable xenon isotopes

In this paper we investigate the hyperfine structure and isotope shift of four near infrared xenon transitions by means of a semiconductor diode laser. Doppler free spectra were obtained by using either a saturation spectroscopy technique in cell or a laser induced fluorescence technique on a collimated atomic metastable beam. The hyperfine coupling constants of ¹²⁹Xe and ¹³¹Xe were determined for the levels 1s₅, 1s₄, 1s₄2, 2p₂, 2p₄ and 2p₆ (Paschen notation). Moreover, a systematic study of the isotope shift was performed for the 1s₃ → 2p₄ and 1s₅ → 2p₆ transitions for which all the stable isotopes ^128–131Xe , ¹³²Xe, ¹³⁴Xe, and ¹³⁶Xe were fully resolved. This revised version was published online in August 2006 with corrections to the Cover Date.     

Submillimeter and infrared spectroscopy on La0.85Sr0.15MnO3

The optical conductivity of La_0.85Sr_0.15MnO₃ single crystals was studied by means of submillimeter and infrared spectroscopy for frequencies cm^-1 and temperatures 10 K < T <300 K. The submillimeter conductivity follows the temperature dependence of the dc-data. The phonon spectrum of La_0.85Sr_0.15MnO₃ changes considerably below K revealing a structural phase transition induced by charge or orbital order. At T =10 K a number of phonon modes can be identified in addition to the room-temperature spectrum. The optical conductivity () in the mid-infrared reveals the characteristics of small polaron absorption. Below the magnetic ordering temperature the polaron binding energy is highly reduced, but the onset of charge order interrupts the formation of free charge carriers with a Drude-like behavior. The frequency and temperature dependence of in this regime qualitatively resembles the small polaron predictions by Millis et al. (Phys. Rev. B 54, 5405 (1996)). Received 5 November 1999     

Laser spectroscopy of radioactive lead and thallium isotopes

By collincar fast beam laser spectroscopy hyperfine structure and isotope shift have been measured of neutron deficient radioactive isotopes of lead (¹⁹⁰Pb,¹⁹¹Pb,¹⁹²Pb,¹⁹³Pb,¹⁹⁴Pb,¹⁹⁵Pb,¹⁹⁶Pb,¹⁹⁷Pb) and thallium (¹⁸⁸Tl¹⁹⁰Tl,¹⁹¹Tl,¹⁹²Tl,¹⁹⁴Tl,¹⁹⁶Tl). Therefrom nuclear magnetic dipole moments, electric quadrupole moments, changes of the mean square charge radii and deformation parameters are deduced and compared with predictions from theory.     

Laser spectroscopy and mass measurements on alkali isotopes

Isotope shifts, spins, hyperfine structures and masses have been measured for the series of the alkali isotopes including the nuclei far from stability. The method of laser spectroscopy and its combinations with rf excitation are described. Some results are discussed, namely the first observation of the red doublet D₁-D₂ of francium, and the study of shell effects and changes of shape with mass and δ〈r ²〉 measurements for Rb and Na isotopes.     

Laser spectroscopy measurements of neutron-rich tellurium isotopes by COMPLIS

Laser spectroscopy based on resonant ionization of laser-desorbed atoms has been used to study the neutron-rich tellurium isotopes with the COMPLIS facility at ISOLDE-CERN. Isotope shifts and hyperfine structures of several neutron-rich Te isotopes: ^120?136Te and ^{123 m?133 m}Te have been measured. From the hyperfine structure we have extracted magnetic and quadrupole moments. Changes in the mean square charge radii have been deduced and their comparison with the known data for the other elements near Z?=?50 is presented. The experimental δ?<?r ²> values are compared with those obtained from relativistic mean field calculations.     

Submillimeter wave esr and far infrared spectroscopy measurements of CuGeO3

Submillimeter wave ESR and far infrared transmission measurements of first inorganic spin-Peierls system CuGeO₃ have been performed using the single crystals. Our new results are discussed in connection with the magnetic properties of the spin-Peierls systems and the recent neutron measurements of CuGeO₃.