Effective coupling constants for beta and gamma transitions in medium and heavy nuclei

Effective coupling constants (g^eff) for favored (but hindered) beta and gamma transitions in medium and heavy nuclei are studied systematically. Experimental g^eff values for the β and γ transitions with parity change are presented, and are analyzed in terms of the susceptibility κ (polarization factor) defined as g^eff=g/(1 + κ). Most of the first forbidden β transitions and E1, M2, M4 gamma transitions are shown to have uniformly g^eff/g=0.2～0.4 and thus κ=3～2. Emphasis is placed upon the problem as to how large the value of susceptibility (or polarizability) due to nuclear spin-isospin core polarization is for the nuclear matter. Theories of the core polarization effects are reviewed, and are shown to predict well the observed susceptibilities κ for the various modes. Discussions are given on higher order effects, couplings with different modes, and mass and multipole dependence in the nuclear core polarization phenomena.     

Neutrino mass effect on the nuclear muon capture

Multipole expansion of the partial transition amplitude in the nuclear muon capture with massive lefthanded Dirac neutrino has been derived. The multipole amplitudes for the partial nuclear transitions are given as the explicit functions of the neutrino mass parameter. As an example, the capture rate, the recoil asymmetry and the neutrino polarization are investigated in terms of these multipole amplitudes. The transversal neutrino polarization provides a connection between theT-violation and the neutrino mass: ifT-odd component in the neutrino polarization is observed, then neutrino must be a massive particle. It turns out that in the capture rate and recoil polarization, the effects due to very small neutrino mass can be proportional to the square ratio of the neutrino mass to its momentum, while the neutrino transversal polarization is proportional to this ratio only. Under the recent limits on the muon neutrino mass, the observable effects inthe partial transition may be below the order of ?10^?3.     

A contribution from collective rotation to ΔI=±1 transitions in the cranking model

The contribution of the orientational polarization of the core to quasiparticle transition amplitudes in deformed nuclei is derived. In the cranked mean-field model, these contributions arise from the coupling of rotational RPA excitations to the quasiparticles. They reduced to the usual core contribution (g_R) for M1 transitions, and give a collective and possibly oscillatory contribution to E2 transitions with ΔI=±1.     

Shell-model analysis of helion and triton inelastic scattering from90Zr including core polarization effects

A microscopic analysis of the inelastic scattering of helions and tritons from⁹⁰Zr is performed using the shell-model wavefunctions and phenomenological effective interactions. Effects of the core polarization are studied assuming a collective model for the core of closed shells. Core coupling parametersA _L , are obtained from the measured electromagnetic transition rate,B(EL). For those transitions for which no meauredB(EL) values are available,A _L values which fit the data have been extracted. The radial forms of both the Gaussian and Yukawa interactions were studied. Effects of the non-locality of the bound states on the predicted cross sections are found to be small. As in the case of proton inelastic scattering, it is found that the valence (direct) contributions are small and the transitions are dominated by core polarization. The strength of the effective interaction required to fit the data is reduced by a factor of two or more when the core polarization contributions are included.     

Phase states and dielectric properties of sodium-potassium niobate solid solutions

The temperature dependence of dielectric constant ? for single crystals of Na_1?xK_xNbO₃ (0.04?x?0.15) is studied for the first time. From the shape of the ?(T) anomalies corresponding to rotational phase transitions, the type of interaction between the order parameters and the polarization is determined. A phenomenological model is developed which adequately describes the experimentally observed sequence of high-temperature (T>300°C) phase transitions, the dielectric anomalies associated with these transitions, and the changes in the phase states under the action of external factors (pressure, electric field).     

Two-photon excitation of Na atoms in a flame by broad-band laser irradiation

With a flashlamp-pumped tunable dye laser the 3S→3D, 3S→4D and 3S→5S two-photon transitions of sodium are excited and the resulting fluorescence radiation at various atomic transitions is detected. The sodium is nebulized into a stoichiometric H₂-O₂-Ar flame at atmospheric pressure and at a temperature of 1800 K. Collisional population exchange between several of the higher Na-levels is found to occur. Saturation and saturation broadening of two-photon transitions are observed. Formulas for two- photon excitation rates in the case of broad-band excitation are derived and show substantial agreement with experiment.     

Messung der zirkularen Polarisation der Inneren Bremsstrahlung von90Y

The circular polarization of the Internal Bremsstrahlung (IB) of⁹⁰Y was measured with a Compton polarimeter according to Beard and Rose. The results are compatible with the theoretical predictions of Ford and Martin [8], who include “detour transitions” in their calculations of the circular polarization. Measurements ofΒ-γ-correlations of the IB of⁹⁰Y are discussed, which suggest the consideration of detour transitions too.     

Electroreflectance of strontium titanate

The room temperature electroreflectance (ER) measurements for cubic SiTiO₃ are reported with particular emphasis on experimental conditions important for consistent reproducible lineshapes. This study includes for the first time a determination of the position of zero band perturbation (flatband) by making use of the even field nature of the ER lineshapes. The ER spectra are dependent upon dc bias, indicating the importance of a knowledge of the flatband position. A Kramers-Kronig analysis is performed and the lineshapes are reported in terms of ΔR/R, Δε₁ and Δε₂. The results in terms of Δε₂ show that the strongest direct transition occurs near 3.8 eV. The weak structure in the 3.4 eV region is due to either indirect transitions or weak direct transitions. Our unpolarized flatband ER spectra give rise to structures which for (110) samples are resolved into contributions from [001] and [12̄10] polarized spectra. In addition to the large oscillations observed above the band gap, weaker oscillatory structure is observed in the range 1.5 to 2.8 eV in the polarized spectra of (110) faced samples. The oscillations for [11̄0] polarization are 180° out of phase with those for [001] polarization.     

Polarization of atomic hydrogen lines upon collision with an electron beam

A technique is described for the analytical calculation of the degree of linear polarization of atomic hydrogen lines formed by several radiative transitions with different polarizations upon excitation by an electron impact. The degree of linear polarization of the line L of the hydrogen atom is calculated as an example. The analytical equations used are derived by the Born method. The results of the analytical calculation are compared with experiment and with other calculations. The effective excitation cross sections and the degree of linear polarization of the H_α and H_β lines of the hydrogen atom are calculated analytically for the case of electron-beam excitation. The results of the analytical calculation of the effective excitation cross section of the H_α line are compared with the available experimental and calculated data.     

Electroreflectance observation of localized and itinerant electron states in NiO

We have observed electroreflectance spectra in NiO at 6 eV which we believe represent transitions from the oxygen 2_p derived valence band to the nickel 4s derived conduction band. We also observe the spectrum seen earlier by McNatt near 4 eV but interpret it differently in terms of transitions from the localized 3d⁸ state to the 4s band. These interpretations are consistent with the recent model of Adler and Feinleib.     

A single wavelength 1339 nm Nd:YAP pulsed laser

The laser oscillating at a weak line of Nd:YAP around 1.3-μm realized though selecting polarization is described. The energy level transitions of Nd:YAP crystal and their polarization properties were analyzed. A thin-film polarizer was adopted to restrain the oscillating of the c-axis strong polarized spectral lines and a reasonable transmittance was designed to suppress the a-axis polarized 1064 nm strong line lasing, and then a-axis polarized 1339 nm pulse laser of 336 mJ for free running mode and 64 mJ for electro-optic Q-switched mode were successfully achieved, corresponding to pulse widths of 180 μs and 35 ns, respectively. This method of selecting polarization to realize weak line oscillating is significant for anisotropic laser crystals doped with Nd³⁺ ions to select the particular transitions.     

Polarization effects on theft values of the beta transitions to155Gd

A good agreement between theory and experiment is achieved if besides the Coriolis force effect, the centrifugal and spin-spin polarization effects are considered in the calculation of the absoluteft values for the ΔN=2 beta transitions¹⁵⁵Eu→¹⁵⁵Gd. An important improvement is also obtained for the first forbidden transitions if the spin-spin polarization effects are taken into account.     

Searches for effects of fundamental-symmetry violation in isomeric nuclear states

The results of broad searches for schemes that are convenient for observing effects of time-inversion-invariance violation (T violation) simultaneously with parity violation (PT violation) in electromagnetic transitions in nuclei are presented. The main problems in observing such effects are discussed. A scheme that seems one of the most promising for this and which relies on measuring the linear polarization of gamma radiation accompanying the deexcitation of isomeric states of nuclei that were oriented by a magnetic field at ultralow temperatures is highlighted.     

Exchange current contributions to parity violating electric transitions revisited

A detailed analysis of possible exchange current contributions to parity violating E1 transitions in nuclear processes is presented and applied to the circular polarization P_γ in thermal n-p photocapture. In agreement with previous claims it is found that significant contributions are not expected.     

On generalizations of the Debye equation for dielectric relaxation

In some previous papers one of us (G.A.K.) discussed dielectric relaxation phenomena with the aid of non-equilibrium thermodynamics. In particular the Debye equation for dielectric relaxation in polar liquids was derived. It was also noted that generalizations of the Debye equation may be derived if one assumes that several microscopic phenomena occur which give rise to dielectric relaxation and that the contributions of these microscopic phenomena to the macroscopic polarization may be introduced as vectorial internal degrees of freedom in the entropy. If it is assumed that there are n vectorial internal degrees of freedom an explicit from for the relaxation equation may be derived, provided the developed formalism may be linearized. This relaxation equation has the form of a linear relation among the electric field E, the first n derivatives with respect to time of this field, the polarization vector P and the first n + 1 derivatives with respect to time of P. It is the purpose of the present paper to give full details of the derivations of the above mentioned results. It is also shown in this paper that if a part of the total polarization P is reversible (i.e. if this part does not contribute to the entropy production) the coefficient of the time derivative of order n + 1 of P in the relaxation equation is zero.     

Experimental study of the resonance radiation group delay in degenerate systems

The dependence of the polarization-and intensity-modulation group delay on the polarization of electromagnetic wave was studied experimentally for different transitions between the hfs components of the ⁸⁷Rb D₁ absorption line. It was found that the polarization-modulation delay strongly depends on the degeneracy structure of resonant transition and, in the general case, on the ellipticity of light-wave polarization. It is demonstrated that the polarization-modulation delay does not occur for the transitions not involving dark states. The polarization delay was studied as a function of the polarization ellipticity angle. The intensity-modulation delay was measured for the resonance radiation to show that it is observed for all ⁸⁷Rb D₁-line transitions and is independent of polarization.     

The effects of the microscopical theory of the Coriolis forces on nuclear beta-decay155Eu →155Gd

The wave functions yielded by the microscopical non-adiabatic treatment of the Coriolis interaction proposed in Dubna by Pyatov, Chernej and Baznat have been used in order to calculate the beta decay observables of some allowed transitions of the¹⁵⁵Eu nucleus. The Coriolis interaction effects are important especially for the absoluteft values (an important improvement is obtained) and for theβ-γ circular polarization correlation.     

Saturation spectroscopy of hydrogen 1-011-011-01lines with a multi-mode cw dye laser

With an intense, broadband multi-mode cw dye laser collisional studies of H_α fine-structure resonances with saturated absorption are extended to He buffer gas pressures larger than 30 mbar (0°C). The broadening and shift of the two prominent H_α(2P?3D) transitions are measured in a (He+4% H) gas discharge. The absolute magnitude and the differences in the width of the lines are explained theoretically by different inelastic fine-structure transfer cross sections which can also be deduced from the pressure effect data. Nuclear polarization of hydrogen atoms by H_α optical pumping and polarization transfer to the H(1S) ground state via Ly-α decay and further applications of the multimode laser are discussed.     

Fluorescence and fluorescence excitation spectra of jet-cooled carbazole

The fluorescence excitation spectra of jet-cooled carbazole molecules at vibrational temperatures of 55 and 80 K and the fluorescence spectrum of these molecules excited by radiation at the frequency of a pure electronic transition are measured. As the vibrational temperature increases, the excitation spectra exhibit a series of lines of the same symmetry, which are caused by the interaction of the active vibration with a subensemble of optically inactive vibrations. The final symmetry of the totally and nontotally symmetric vibrations is determined from the shape of the rotational contours of the lines of vibronic transitions. The values of a decrease in the frequency of the nontotally symmetric vibrations in the first excited electronic state S ₁ due to their interaction with the electronic state S ₂ are calculated to be up to 100 cm^?1. The frequencies of the pure electronic transitions in the absorption and fluorescence spectra coincide with each other and are equal to 30809 cm^?1, the frequencies of vibrations in the ground state S ₀ exceeding the frequencies of the corresponding vibrations in the excited state S ₁. The degree of polarization of the integral fluorescence is determined for a series of vibronic transitions of the a ₁ and b ₂ final symmetry that are observed in the fluorescence excitation spectra, and the contribution of the intensity with the borrowed polarization θ_⊥ to the integral fluorescence is calculated. It is found that the intensity θ_⊥ is higher for the transitions of the b ₂ symmetry and can reach ≈50%.     

In-beam conversion electrons from 141Pr, 143Pm, 144Pm and 145Pm excited by (α, xn) and (p,n) reactions

Electromagnetic transitions between low-lying states in the odd proton nuclei ₅₉¹⁴¹Pr₈₂, ₆₁¹⁴³Pm₈₂, ₆₁¹⁴⁴Pm₈₃ and ₆₁¹⁴⁵Pm₈₄ with neutron numbers N ≈ 82 were studied by means of in-beam electron-gamma spectroscopy. The triple-focusing electron spectrum selector (TESS) was used to measure in-beam conversion electrons. The TESS, giving very good electron line spectra with small background, was found to be very powerful for in-beam spectroscopy. Accurate values for the internal conversion coefficients (ICC) were obtained by measuring simultaneously both conversion electrons and γ-rays. M2, E3 and some other multipolarities were uniquely assigned from the ICC for the γ-transitions between low-lying states. Properties of these transitions and energy levels are discussed. Analyses of the M2 and E3 transition rates gave, respectively, an isospin-spin (magnetic) core polarization effect and an octupole core polarization effect. The l-forbidden M1 transitions were analyzed in terms of the tensor terms.