High-spin negative parity states in doubly even Hg,Pt and Os nuclei

A systematic study of the level structure of ²⁰⁰Hg, ¹⁹⁸Hg, ¹⁹⁶Hg, ¹⁹⁴Pt, ¹⁹²Pt, ¹⁹⁰Pt, ¹⁸⁸Os, ¹⁸⁶Os and ¹⁸⁴Os has been performed by means of (α, 2nγ) and (p, 2nγ) in-beam γ-ray spectroscopy. Much new information has been obtained about the individual level spectra, and arguments based on level energy and population intensity systematics have been used to trace the behaviour of interesting spectral features through this series of transitional nuclei. Of particular interest is a 5^?, 7^?, 9^? … sequence of levels which appears to be a recurring feature in the spectra of the doubly even Pt and Hg nuclei in the mass range A = 190–200. These negative parity levels are connected by enhanced E2 transitions and they are very strongly populated in the de-excitation of the residual nuclei formed in (α, 2n) reactions. It is proposed that the 5^?, 7^?, 9^? … sequences constitute rotation-aligned bands analogous to the decoupled bands identified by Stephens and co-workers in odd-A transitional nuclei. In the doubly even nuclei, the bands may arise from the coupling of an $\text{i}\text{13}\text{2}$ neutron with a low-j neutron partner (from the $\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, $\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and $\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ orbitals). Negative parity levels in the Os nuclei are populated much less strongly in the (α, 2nγ) reactions. While 5^? levels corresponding to those in the Pt and Hg nuclei appear to be fairly well established in ¹⁸⁶Os, ¹⁸⁸Os (and ¹⁹⁰Os), it is not yet clear whether the 5^?, 7^?, 9^? … band sequence extends into the Os nuclei.     

Lysine IR emission spectrum excited by moderately intense visible radiation

The excitation of IR emission is observed for thin films illuminated by continuous visible light in the absence of light absorption in the sample. The effect is demonstrated by the example of the lysine molecule and explained by the resonant combined action of optical photons with frequencies ω_i and ω_j, whose differences ω_i?ω_j=Ω coincide with the frequencies of the lysine vibrational modes.     

Coupled mode behavior of the soft E(TO) phonon of Pb(Ti1-x,Zrx)O3 and (Pb1-3x2, Lax)TiO3

We report the temperature dependence of the low frequency part (ω < 100 cm^?1) of the Raman spectra of the Pb(Ti_1-x, Zr_x)O₃ and $\text{(}\text{Pb}{}_{\mathrm{<mtext>1-</mtext><mtext>3x</mtext><mtext>2</mtext>}}$, La_x)TiO₃ systems. The spectra indicate a coupled mode behavior between the soft E(TO) phonon and a mode which produces an additional band in the spectra. We discuss the possibility that the additional band might be due to zone boundary tranverse acoustical phonons which couple to the q ～ 0 soft E(TO) mode because of the disorder existing in the systems.     

Free carrier absorption in quantizing magnetic fields: Nonpolar optical phonon scattering

A quantum theory of free carrier absorption in nondegenerate semiconductors and in strong magnetic fields which was previously developed to treat the case when acoustic phonon scattering dominates the free carrier absorption process [1] is extended to treat the case when nonpolar optical scattering is important. When the electromagnetic radiation field is polarized parallel to the direction of the applied magnetic field, results are obtained which are similar to those when acoustic phonon scattering is dominant. The free carrier absorption is an oscillatory function of the magnetic field which on the average increases in magnitude with the magnetic field. However, more structure in the free carrier absorption occurs when nonpolar optical phonon scattering dominates. This is due to the fact that there are two periods in the oscillatory magnetic field dependence associated with the emission or the absorption of optical phonons during the intraband transitions. When the cyclotron frequency exceeds the sum of the photon and optical phonon frequencies, i.e. ω_c > θ + ω_o, the free carrier absorption is predicted to increase linearly with magnetic field when ?ω_c? k_BT. The magnetic field dependence of the free carrier absorption can be explained in terms of phonon-assisted transitions between the various Landau levels in a band involving the emission and absorption of optical phonons.     

Theoretical calculation of the entropy change associated with substitutional anion defects in KCl

The entropy change S_d accompanying the substitution of a Cl^? ion in KCl by a F^?, Br^? or I^? ion has been calculated by a method that involves the whole phonon spectrum of the perfect crystal. The results are: $\text{S}{}_{\mathrm{d}}\text{k}\text{= -0.909}$ for KCl:F^?, 1.897 for KCl:Br^? and 4.055 for KCl:I^?. These figures are compared with the results obtained by approximate methods that have been used previously.     

Inverse solutions to the inelastic scattering problem

Exact inverse solutions to the integral equation $\text{φ(r}{}_{\mathrm{s}}\text{|r}{}_0\text{, k) = ?}{}_{\mathrm{D}}{}^3\text{f (r, ω)g(r|r}{}_0\text{, k)g(r|r, k)d}{}^3\text{r}$, where g(r|r_j, k); j = 0 or s is the free space Green function, are derived in plane and cylindrical coordinates for fixed ω. These solutions allow an inelastic scattering potential f(r, ω) which is of compact support r ? $\text{D}$³ to be recovered from scattering data collected over the surfaces of a plane and cylinder respectively.     

Stimulated Raman spectra of a strong bichromatic field interacting with a three-level atom

We have studied the stimulated Raman spectra arising from the interaction of a three-level atom with two strong electromagnetic fields whose initially populated modes ω _a and ω _b are in resonance with the two atomic transition frequencies. The Green's function formalism has been used in the limit of high photon densities to calculate the excitation spectra near the frequencies ω = ± ω _ab = ± (ω _a - ω _b ). Expressions are derived for the relative intensities, which describe, apart from the usual Raman peak at the frequency ω = ω _ab , four pairs of lorentzian lines peaked at the frequencies ω - ω _ab = ± Ω _a /√2, ± Ω _b /√2, ± Ω and ± 2Ω, respectively, and having spectra widths of the order of 3γ₀/4. The parameter Ω is defined as Ω² = (Ω _a ² + Ω _b ²)/2, where Ω _a and Ω _b are the Rabi frequencies of the two laser fields and γ₀ is the spontaneous emission probability. Numerical calculations for selected values of the Rabi frequencies are graphically presented and discussed. Conditions have been established for which Raman gain processes are anticipated to take place.     

Microwave spectral study of 2-fluorophenol: cis conformer

The microwave spectra of 2-fluorophenol and its deuterated species have been observed and analyzed in the frequency ranges 12.5–18.0 GHz (KU band) and 21.5–26.0 GHz (K band) in the ground vibrational state at room temperature. For the normal species, the radio frequency-microwave double resonance spectrum has been recorded in the frequency range 30.0–38.0 GHz. Three rotational and five quartic centrifugal distortion constants for the normal species, $\text{A}\text{?}\text{= 3337.86 ± 0.02}$, $\text{B}\text{?}\text{= 2231.92 ± 0.01}$, $\text{C}\text{?}\text{= 1337.52 ± 0.01}$, d_J = (3.5 ± 2.9) × 10^?4, d_JK = (?4.9 ± 1.5) × 10^?3, d_K = (?3.2 ± 1.0) × 10^?3, d_WJ = (?2.0 ± 1.0) × 10^?7, d_WK = (2.6 ± 0.8) × 10^?6 (in MHz), and three rotational constants for the deuterated species, $\text{A}\text{?}\text{= 3324.70 ± 0.03}$, $\text{B}\text{?}\text{= 2177.95 ± 0.03}$, $\text{C}\text{?}\text{= 1315.96 ± 0.03}$ (in MHz), have been obtained. Consideration of the r_s coordinate of the hydroxyl hydrogen atom leads to the assignment of the spectra to the cis conformer of the molecule. An r₀ structure for the cis conformer has been proposed. The nonbonded OH ? F distance is lower by about 0.3 Å than the sum of the van der Waals radii.     

Evidence of an induced polariton branch in CuCl by hyper-Raman scattering

We study the renormalization of the dispersion of excitonic polaritons, induced by a strong light source at frequency ω_l. Since biexcitons with energy E_Bi show a giant oscillator strength, this renormalization effect is located around frequencies Ω such as $\text{h}\text{?}\text{Ω +}\text{h}\text{?}\text{ω}{}_{\mathrm{l}}\text{= E}{}_{\mathrm{Bi}}$. It gives rise to an induced polariton branch, the dispersion of which depends on the frequency of the exciting light source. It manifests itself through additional emission lines in hyper-Raman scattering processes.     

KL0-KS0 transmission regeneration on deuterons and neutrons in a momentum range of 10–50 GeV/c

The energy dependence of the K_L⁰-K_S⁰ transmission regeneration amplitudes on deuterons and neutrons in the momentum region 10–50 GeV/c is determined. The moduli of the modified transmission amplitudes are momentum dependent. These dependences are fitted by the expression A_jp^?nj, where A_j and n_j (j = d, n) are constants:

$\text{A}{}_{\mathrm{<mtext>d</mtext>}}\text{=2.88 ±0.04}\text{mb}\text{, n}{}_{\mathrm{<mtext>d</mtext>}}\text{=0.546±0.030,}\text{for deuterons}\text{,}$

$\text{A}{}_{\mathrm{<mtext>n</mtext>}}\text{=1.97 ±0.14}\text{mb}\text{, n}{}_{\mathrm{<mtext>n</mtext>}}\text{=0.530±0.019,}\text{for neutrons}\text{,}$

The amplitude phases do not depend on the kaon momentum and are equal to $\text{?}{}_{\mathrm{<mtext>d</mtext>}}\text{= (?130.9 ± 2.7)°}$?_n = (?132.3 ± 1.7)°. The mean value of the ratio of the total cross-section differences for K⁰ and K⁰ interactions with neutrons and protons is determined. The residues of the partial ω and ? amplitudes, which contribute to the kaon-nucleon interaction amplitudes, are also obtained.     

Oblate ground-state shapes of 11 h 189Pt and 2.8 d 191Pt

With nuclear orientation on $\text{11}\text{h}\text{3}\text{2}{}^{\mathrm{?189}}\text{Pt}\text{, 2.8}\text{d}\text{3}\text{2}{}^{\mathrm{?191}}\text{Pt}$ and $\text{4.0}\text{d}\text{13}\text{2}{}^{\mathrm{<mtext>+\; 195\; </mtext><mtext>m</mtext>}}\text{Pt}$ in Os and NMR on oriented ¹⁸⁹Pt and ¹⁹¹Pt in Fe electric and magnetic hyperfine splitting frequencies were measured. The nuclear moments are deduced to be: ¹⁸⁹Pt: |μ| = 0.434(9) μ_N, Q = ?0.65(26) b; ¹⁹¹Pt: |μ| = 0.500(10) μ_N, Q = ?0.64(26) b; ^195mPt: Q = +1.42(60)b. The negative spectroscopic ground-state quadrupole moments of ¹⁸⁹Pt and ¹⁹¹Pt must be due to oblate ground-state deformations, thus indicating that the prolate-oblate phase transition in Pt is located at A < 189.     

Phonon singularities on volt-ampere curves of niobium point contacts

The volt-ampere curves and their second derivatives were studied for niobium point contacts at low temperatures in the voltage range corresponding to the characteristic phonon energies. It was found that while for the dirty contacts in the normal state no PC spectra of phonons could be detected, in the superconducting state there were singularities in the I–V curves corresponding to maxima either in the first or in the second derivatives. The singularities observed were due to the energy dependence of the excess current. We suppose that the origin of these singularities is due to the inelastic transitions of electrons between chemical potentials of Cooper pairs at both sides of the contact, which differ in energy by eV. These transitions are possible if ξ(0) ? d ≈ Λ_?, (ξ(0) being the coherence length; d, the contact diameter; $\text{Λ}{}_{\mathrm{?}}\text{= (l}{}_{\mathrm{i}}\text{·l}{}_{\mathrm{?}}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, where l_i and l_? being the elastic and inelastic electron mean free paths, respectively).     

Adsorption,coadsorption, and reactivity of sodium and nitric oxide on Ag(111)

The adsorption, desorption, and surface structural properties of Na and NO on Ag(111), together with their coadsorption and surface reactivity, have been studied by LEED, Auger spectroscopy, and thermal desorption. On the clean surface, non-dissociative adsorption of NO into the a-state occurs at 300 K with an initial sticking probability of ~0.1, saturation occurring at a coverage of $\text{~}\text{1}\text{20}$. Desorption occurs reversibly without decomposition and is characterised by a desorption energy of E_d ~ 103 kJ mol^?1. In the coverage regime 0 < θ_Na < 1, sodium adsorbs in registry with the Ag surface mesh and the desorption spectra show a single peak corresponding to E_d ~ 228 kJ mol^?1. For multilayer coverages (1 < θ _Na < 5) a new low temperature peak appears in the desorption spectra with E_d ~ 187 kJ mol^?1. This is identified with Na desorption from an essentially Na surface, and the desorption energy indicates that Na atoms beyond the first chemisorbed layer are significantly influenced by the presence of the Ag substrate. The LEED results show that Na multilayers grow as a (√7 × √7) R19.2° overlayer, and are interpreted in a way which is consistent with the above conclusion. Coadsorption of Na and NO leads to the appearance of a more strongly bound and reactive chemisorbed state of NO (β-NO) with E_d ~ 121 kJ mol^?1. β-NO appears to undego surface dissociation to yield adsorbed O and N atoms whose subsequent reactions lead to the formation of N₂, N₂O, and O₂ as gaseous products. The reactive behaviour of the system is complicated by the effects of Na and O diffusion into the bulk of the specimen, but certain invariant features permit us to postulate an overall reaction mechanism, and the results obtained here are compared with other relevant work.     

Exact derivative interband dielectric function at Van Hove singularities

Interpretations of derivative spectra obtained by wavelength or thermal modulation have been based on universal lineshape functions that include only the resonant term, $\text{(ω}{}_{\mathrm{g}}\text{? ω ?iη)}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$, obtained from differentiating ε(ω) with respect to ω or ω_g, and that neglect the (ω + iη)^?2 prefactor. We find the following differences between the approximate universal lineshape functions and the exact results obtained by including the nonresonant terms. dε/dω and dε₂/dω are no longer simply related to each other; two entirely different functions are obtained. Wavelength and temperature modulation no longer have identical lineshapes. Either dε₁/dω or dε₂/dω has a resonant derivative lineshape according to whether j is even or odd, respectively, in contrast to the approximate universal function, which has no zeros, dε₁/dω for a pure M₁ singularity has positive and negative peaks of approximately equal strength, which would agree with the experimental results without invoking hyperbolic excitons (admixtures of M_j and m_j+1 lineshapes). On the other hand, the nonexcitonic exact result fails to reproduce other experimental features. At the very least, our results call into question the extraction of numbers from detailed curve fits to the approximate functions.     

Rigorous spin tests from angular distribution of single two-body decays

We extend to the several-amplitude decays j→j₁+j₂, (j?j₁+j₂,j₁+j₂?2) the rigorous spin tests given by Doncel, Michel and Minnaert for the usual one-amplitude strong decays, in quadrupole and quadrupole-hexadecapole spaces. We also derive spin tests in dipole-quadrupole space for the parity violating decays $\text{j →}\text{1}\text{2}\text{0}\text{and}\text{j →}\text{1}\text{2}\text{1}\text{2}$.     

Specific features of the electronic structure of cerium and its 4d and 5d partners in CeM2 Laves phases (M=Fe, Co, Ni, Ru, Rh, Os, Pt, Mg, Al)

The x-ray line shift method has been used to study the electronic state of Ce (the 4f population) and of its 4d and 5d partners in the CeM₂ Laves phases (M=Fe, Co, Ni, Ru, Rh, Os, Pt, Mg, Al). It is shown that the valence of Ce in CeM₂ decreases monotonically from the limiting value m≈3.35 to m≈3 with decreasing intracrystalline compression of Ce atoms. The population of the outer 4d and 5d orbitals of Ru, Rh, and Os in the Laves phases has been found to be larger than that in metals. Fiz. Tverd. Tela (St. Petersburg) 40, 1397–1400 (August 1998)     

Study of the reactions 118Sn(d,t) and98Mo(d,t): (I). Spectroscopy of 117Sn and 97Mo

The vector analyzing power and differential cross section have been measured at a deuteron energy of 12.0 MeV for ${}^{118}\text{Sn}\text{(}\text{d}\text{,}\text{t}\text{)}$ transitions to six states of ¹¹⁷Sn (E_x = 0.0, 0.16, 0.31, 0.71, 1.02 and 1.18 MeV), for ${}^{98}\text{Mo}\text{(}\text{d}\text{,}\text{t}\text{)}$ transitions to eight states of ⁹⁷Mo (E_x = 0.0, 0.68, 0.72, 0.89, 1.12, 1.28, 2.39 and 2.52 MeV), and for ${}^{118}\text{Sn}\text{(}\text{d}\text{,}\text{d}\text{)}\text{and}{}^{98}\text{Mo}\text{(}\text{d}\text{,}\text{d}\text{)}$. Deuteron optical model potentials were obtained from analysis of the elastic scattering measurements, and were used in a DWBA analysis of the $\text{(}\text{d}\text{,}\text{t}\text{)}$ results. Comparison of the measurements and DWBA predictions for σ(θ) and for iT₁₁(θ) allows unambiguous determination of tl_n and j_n for all ¹¹⁸Sn(d, t) and most ⁹⁸Mo(d, t) transitions. Differences in the triton energy relative to the Coulomb barrier cause marked qualitative differences in the measured cross sections and analyzing powers between ${}^{118}\text{Sn}\text{(}\text{d}\text{,}\text{t}\text{)}\text{and}{}^{98}\text{Mo}\text{(}\text{d}\text{,}\text{t}\text{)}$ transitions of the same l_n and j_n.     

Magnetovolume effect in transition metal-metalloid amorphous alloys

The thermal expansion, spontaneous volume magnetostriction ω_s, forced volume magnetostriction $\text{(}\text{?ω}\text{?H}\text{)}$ and Young's modulus of amorphous Fe-B, Fe-P, Co-B and (Fe-M)₇₇Si₁₀B₁₃ (M = Cr, Mn, Co, Ni) alloys have been measured to make clear the magnetovolume effect in transition metal-metalloid amorphous alloys. The thermal expansion coefficient α, ω_s and $\text{(}\text{?ω}\text{?H}\text{)}$ are dependent on the number of d-electrons per transition metal atom n_eff calculated based on the charge transfer model. The n_eff vs. α, ω_s and $\text{(}\text{?ω}\text{?H}\text{)}$ curves are quite similar to the corresponding curves in fcc alloys. The maxima in those curves are, however, found at n_eff ≈ 8.2 for the amorphous alloys in contrast with n_eff ≈ 8.7 for the fcc Fe-Ni alloys. On the other hand, Young's modulus measured under the saturation of magnetization is governed by the molar volume, irrespective of n_eff. The magnetovolume effect in transition metal-metalloid amorphous alloys is discussed in connection with the instability of ferromagnetism of amorphous Fe.     

Hydrodynamics of an n-component phonon system

The dynamic properties of an n-component phonon system in d dimensions, which serves as a model for a structural phase transition of second order, are investigated. The symmetry group of the hamiltonian is the group of orthogonal transformations $\text{O}$(n). For n ≥ 2 a continuous symmetry is broken for T<T_c, where T_c is the transition temperature. We derive the hydrodynamic equations for the generators of this group, the $\text{1}\text{2}\text{n (n ? 1)}$ angular-momentum variables. Besides the usual hydrodynamics of a phonon system, there are $\text{1}\text{2}\text{n (n ? 1)}$ additional independent diffusive modes for T > T_c. In the ordered phase we find 2 (n ? 1) propagating modes with linear dispersion and quadratic damping. Formally the hydrodynamics is similar in the isotropic Heisenberg ferromagnet (n = 2) or the isotropic antiferromagnet (n ≥ 3). The relaxing modes for T < T_c require special care. We study the critical dynamics by means of the dynamical scaling hypothesis and by a mode-coupling calculation, both of which give the critical dynamical exponent $\text{z =}\text{1}\text{2}\text{d}$. The results are compared with the 1/n expansion. It is shown that for large n there is a non-asymptotic region characterized by an effective exponent $\text{z}\text{?}\text{= φ/2ν}$, where φ is the crossover exponent for a uniaxial perturbation, and ν the critical exponent of the correlation length.     

Cabibbo Universality,renormalization, and the Z vector boson mass

Using the most recent data on the ft-values of the 0⁺ → 0⁺ decays ¹⁴O, ^26mAl and ³⁵Cl, the hyperon β-decays, and the K_e3⁺ rate, we determine the following limits (95% confidence level): Cabibbo angle sin θ > 0.226, intermediate vector boson mass M_Z > 25 Gev (for four quarks with integral charges) or M_Z > 110 GeV (three colored quartets), K_e3⁺ form factor $\text{?}{}_{\mathrm{+}}\text{(0) < 0.98}$.