Precision measurement of the hyperfine structure of Lu175 with the atomic beam magnetic resonance method

The hyperfine structure separations of both doublet states² D _3/2 and² D _5/2 of the ground state configuration 6s ² 5d of Lu¹⁷⁵ have been remeasured with high precision using the atomic beam magnetic resonance method. Magnetic dipole transitions between Zeeman components of the hfs levels were induced applying Ramsey's technique of separated oscillatory fields whenever the field dependence of the resonances was small enough. The hfs intervals at zero field and hfs interaction constants were derived from the measurements. The constants were then corrected for hfs perturbations between the two levels of the doublet. Configuration interaction has been taken into account for the calculation of the dipole matrix elements. The corrected hfs constants are:J=3/2:A=194.332921 (300) MHzB=1511.396 267 (320) MHzC=?70 (19) HzJ=5/2:A=146.776 472 (138) MHzB=1860.656132 (840) MHzC=913 (162) HzD=?16 (24) Hz A quadrupole hfs anomaly between Lu¹⁷⁵ and Lu^176m was not found when comparing the following two ratios: Lu¹⁷⁵:B(5/2)/B(3/2)=1.2310850 (16) Lu^176m :B(5/2)/B(3/2)=1.2310818 (30). So far we have not succeeded in computing an octopole moment from the twoC-factors for the terms² D _3/2,5/2 because the influence of higher configurations could not sufficiently be considered.     

Optical absorption zeeman spectroscopy of rare earth orthochromites

The optical absorption spectrum of Er³⁺ in ErCrO₃ in the phasesΓ ₁,Γ ₂ andΓ ₄ has been studied as a function of temperature and applied magnetic field. The experimental data for the Er³⁺ ground doublet splitting are analyzed using a single ion molecular field approach. The analysis shows that the Cr — Er interaction is predominantly antisymmetric exchange, the magnetic dipole-dipole interaction being an order of magnitude smaller. The Er — Er interaction is of exchange as well as of dipolar origin.     

AgGaSe2 : A highly photoconductive material

High resistivity single crystals of AgGaSe₂ were grown by the horizontal Bridgman technique. The near band edge photoconductivity of the grown crystal at room temperature was found to be up to 2×10⁴ times higher than the dark conductivity, under the illumination of 10⁻³ W/cm². The photoconductivity spectrum consists primarily of three peaks, which are attributed to the transitions from Γ₇(A), Γ₆(B) and Γ₇(C) states of valence band to the conduction band Γ₆. The crystal field splitting and the spin-orbit splitting were determined from these peak energy positions of the photoconductivity spectrum.     

In search of scalar gluonium

We discuss a scalar meson coupled strongly to gluons. Radiative decays of the J/ψ are taken as a source of gluons so that our aim is to calculate Γ(J/ψ→σγ), where σ is the presumed scalar gluonium. We use QCD sum rules to find both 〈0|α_sG_μν^aG_μν^a|σ〉 (where G_μν^a is the gluon field strength tensor) and Γ(J/ψ→σγ) in terms of 〈0|α_sG_μν^aG_μν^a|σ〉. The final prediction for the width is expected to be valid within a factor of two and gives $\text{Γ(}\text{J}\text{/ψ→σγ→}\text{two pions in S-wave}\text{+ γ) ? 25}\text{eV for}\text{m}{}_{\mathrm{\sigma }}\text{= 700}\text{MeV}$. Non-perturbative QCD naturally explains the observed asymmetry between scalar and pseudoscalar states in the radiative decays of the J/ψ. Some general remarks on gluonium in QCD are made.     

Zur Rumpfpolarisation des Rb-Atoms: Hyperfeinstruktur des 72 P 1/2-Terms von Rb85

The hyperfine structure splitting of the 7² P _1/2 state of Rb⁸⁵ has been investigated with optical double resonance spectroscopy. The results are:v _F=3?F=2=52.95(6) Mc/s,A _J=1/2=17.65(2) Mc/s,g _J (7² P _1/2, Rb)=0.6668(1). From the hfs interaction constants of the 7² P multiplett a 12% core polarization contribution to the magnetic hfs of the 7² P _3/2 state can be deduced. Comparison is made between the values of 〈r ^?3〉 calculated from either the magnetic hfs or the² P fine structure separation.     

Raman scattering in monodomain RbCoF3

Polarized Raman spectra are reported for scattering from a single oriented antiferromagnetic domain in RbCoF₃. Monodomain samples were achieved by the application of a small [100] uniaxial stress. Spectra were recorded at 2 K using non-absorbed, orange laser light. The D_4h symmetry assignments for the principal features are: 34(Γ⁺₅), 335 (Γ⁺₁ and Γ⁺₁), 420 (Γ⁺₁), 950 (Γ⁺₃) and 1050 cm^-1 (Γ⁺₁). These results are not consistent with the prediction of previous models for magnetic exciton scattering.     

Laser phase fluctuations in a four-level atomic system in N-configuration

We discuss here the effect of laser phase fluctuations on coherent spectroscopy of four-level N-system interacting with a trichromatic radiation field of frequencies Ω _i , (i = 1?3). The laser phase variables are described by the Wiener-Levy diffusion process to specify the bandwidths (Γ _i ) and cross-correlations (Γ _ij ) that may exist between pairs of laser fields. A general formalism based on the master equation and theory of multiplicative stochastic processes is developed and used to study three-photon and (2+1)-photon absorptive resonances in model N-system of ⁴⁰Ca⁺ ion. It is observed that the resonances are suppressed or broadened by all Γ _i ,(i = 1?3), while their revival is dependent only on Γ ₁₂ and Γ ₂₃, and yet the revival is only partial even when the relevant fields are critically correlated. In contrast Γ ₁₃ is observed to deteriorate the absorptive resonances. The distinctive features of the steady state and time dependent behavior of the system under three-photon and (2 + 1)-photon resonance conditions and for fluctuating fields are discussed.     

Exchange currents in electric transitions and the rôle of siegert's theorem: A case study in deuteron photodisintegration

The hyperfine structure (hfs) splittings of the metastable 1s2s ³ S ₁ state of⁷Li⁺ have been measured with combined laser optical pumping and microwave resonance. A lowenergy Li⁺ ion beam, optically excited by an intersecting laser beam, passed a waveguide where radio frequency transitions were induced. The resulting population transfer among the hfs levels of the³ S ₁ was detected via the change in intensity of the fluorescence light from a second crossing region of laser light and ion beam located past the waveguide. The magnetic hfs constantA(⁷Li⁺, 1s2s ³S₁) was measured and compared with theory. A deviation of the two transition frequenciesν(F=3/2?F=5/2) andν(F=1/2?F=3/2) from the interval rule is due to a depression of theF=3/2 hfs sublevel, caused by mixing of the 2³ S ₁ and 2¹ S ₀ states via hyperfine interaction. This shift was never observed so far in a two-electron spectrum, because of absence ofI>1/2 isotopes in He, the only two-electron atom investigated spectroscopically with high precision. The size of the shift is in fair agreement with a theoretical estimate.     

Equation of state and quantal crossover of the XY model in a longitudinal magnetic field

The equation of state of the XY model in a longitudinal (Γ) and transverse field (B) is investigated in the vicinity of a multicritical point (Γ_c, T =0) using the renormalization group method developed recently by the author and K. Walasek. For Γ = Γ_c a quantal crossover behaviour of the form H = M_{R³ψ (z)} is obtained, where H ～ B, M_R denotes the transverse magnetization, z ～ TM_R^?/βq, while ?,β_q are crossover and multicritical exponents, respectively.     

EPR Spectroscopy of Mercury-Organic Compounds with Nitroxide Radicals

Intramolecular electron spin exchange as a function of temperature, solvent viscosity and polarity has been studied by X-band electron paramagnetic resonance (EPR) spectroscopy for two nitroxide biradicals containing mercury-organic groups in the bridge connecting two 1-oxyl-2,2,6,6-tetramethylpiperidine-3,4-ene-nitroxide rings, R. The temperature dependence of the isotropic hyperfine splitting (hfs) constant a ^N and the exchange integral value |J/a| of the biradicals were measured from EPR spectra and subsequently analyzed comparing to a ^N and a ^Hg hfs constants of ClHgR radical dissolved in the same solvents. In all cases, the interaction of solvent molecules (SM) with >N–O fragments of nitroxide rings led to a slight decrease in a values with increasing temperature. The |J/a| value varied slightly with temperature T changes. The changes of |J/a| are much less comparing to those with variation of the solvent polarity. The interaction between SM and Hg atoms inside the bridge is observed and discussed.     

Determination of theg j -factor in the72 P 3/2-state of133Cs by optical double resonance in a strong magnetic field

The hfs in the 7² P _3/2-state of¹³³Cs has been investigated by optical double resonance in a strong magnetic field. From the positions of the magnetic dipole transitions Δm _j =± 1, Δm _i =0 the magnetic hfs coupling con slanta (7² P _3/2)=16.591(25) MHz and theg _j -factorg _j (7² P _3/2)=1.33410(15) could be derived. Contrarily to recent measurements,g _j agrees well with the value calculated from the Lande formula.     

Core polarization of the133Cs atom by the 7p electron

The hfs of the 7² P _1/2 state of Cs has been measured by optical double resonance yieldingA(7² P _1/2,¹³³Cs)=94.35 (4) MHz. The core polarization contribution to the hfs and the value 〈r ^?3〉 _j =2.54 · 10⁺²⁴ cm^?3 of the 7p electron of Cs has been calculated from the experimental data and was compared with current theories indicating still an appreciable uncertainty in the atomic wave functions of this one-electron atom.     

Van Vleck paramagnetism of the thulium garnet Tm3Al5O12

The magnetic susceptibility of the garnet-type single crystal Tm₃Al₅O₁₂ exhibits the typical Van Vleck temperature independent paramagnetism below ≈8 K. The temperature dependence of the susceptibility over the range 2.0-300 K has been analyzed on the assumption that the cubic crystal-electric-field dominates the energy level on ³H₆ (J=6) ground multiplet for Tm³⁺ ion having 12-electrons in 4f shell. The ground state of the ³H₆ is nonmagnetic with Γ₂ singlet, avoiding the Kramers doublet. The energy separation between Γ₂ and the first excited state Γ⁽²⁾₅ triplet is evaluated to be 68.0 K. The whole energy interval Δ between Γ₂ and the highest state Γ₁ in ³H₆ is estimated to be 339.5 K.     

Cluster fermionic Ising spin glass model with a transverse field

The fermionic Ising spin glass (SG) model in the presence of a transverse magnetic field Γ is studied within a cluster mean field theory. The model considers an infinite-range interaction among magnetic moments of clusters with a short-range ferromagnetic intracluster coupling J₀. The spin operators are written as a bilinear combination of fermionic operators. In this quantum SG model, the intercluster disorder is treated by using a framework of one-step replica symmetry breaking (RSB) within the static approximation. The effective intracluster interaction is then computed by means of an exact diagonalization method. Results for several values of cluster size n_s, Γ and J₀ are presented. For instance, the specific heat can show a broad maximum at a temperature T^∗ above the freezing temperature T_f, which is characterized by the intercluster RSB. The difference between T^∗ and T_f is enhanced by Γ, which suggests that the quantum effects can increase the ratio T^∗/T_f. Phase diagrams (T versus Γ) show that the critical temperature T_f(Γ) decreases for any values of n_s and J₀ when Γ increases until it reaches a quantum critical point at some value of Γ_c.     

Measurement of the transverse Doppler shift using a stored relativistic7Li+ ion beam

We have performed for the first time precision spectroscopy on a coasting fast⁷Li⁺ ion beam in a storage ring. The ion beam moving with 6.4% speed of light was first electron cooled and then merged with two counterpropagating laser beams acting on two different hyperfine transitions sharing a common upper level (λ-system). One laser was frequency locked to thea ₃ ¹²⁷J₂ hfs frequency component established as a secondary frequency standard at 514 nm. The second laser was tuned over theλ-resonance, which was recorded relative to¹²⁷J₂ hfs components. This experiment is sensitive to the time dilation in fast moving frames and will lead to new limits for the verification of special relatively. The present status of the experiment and perspectives in accuracy are discussed.     

Averaged local field intensities in composite films

The photophysical properties of molecules adsorbed in composite films (e.g. surface island films) depend on the local electromagnetic field within the film. The ratio between the average field intensity 〈|E|²〉 in the film and the intensity |E_I|² associated with the incident field is a measure of the electromagnetic contribution to the surface influence on molecular photophysical phenomena. This ratio depends on the film composition and morphology, on the dielectric properties of the pure components making the film and on the frequency, direction and polarization of the incident radiation. Calculations of this ratio as a function of these parameters for several models of composite films are presented. Image interactions and retardation effects as well as radiative damping and finite size contributions to the dielectric response of the films are taken into account. In addition, an estimate of the field inhomogeneity within the film is obtained by calculating also the ratio 〈|E|²〉_shell/|E_I|² associated with the field in thin shells surrounding the dielectric particles which constitute the film.     

Experimental evidence for far configuration mixing effects on off-diagonal hfs interaction between the (3d+4s) N+2 configurations of free atoms

In our systematic investigations on the hyperfine structure (hfs) of high lying metastable states in 3d-shell atoms we have found evidence for an extraordinary strong far configuration mixing effect on off-diagonal matrix elements between configurations. Using theABMR-LIRF method the hfs of (3d ² 4s ²)³ P ⁴⁷Ti, (3d ³ 4s ²)⁴ P ⁵¹V (3d ⁵ 4s ²)⁴ G ⁵⁵Mn and (3d ⁶ 4s ²)³ H ⁵⁷Fe has been measured. Values found for the effective radial parameters \(a^{k_s k_l } \) of the magnetic dipole interaction disagreed up to 300% with those known from hfs measurements of lower lying multiplets of the same configuration, even when intermediate coupling and electrostatically correlated second order hfs effects within each of the configurations are taken into account. We suggest that the main part of these discrepancies can be explained, if two-body core polarization is considered, which screens the ordinary one-body core polarization parametera _3d ¹⁰ . Preliminary values for the corresponding parameters are given.     

Missing mass analysis of the A−2 at 6.0 GeV/c

The missing mass spectrum in the region of the A^?₂ has been measured in the reaction π^?p→X^?p at 6.0 GeV/c in the interval 0.27 <|t|<0.42 (GeV/c)², with an optical spark chamber system which simultaneously observed the decay X^?→ηπ^?. A signal of 230 events above background per five MeV interval is observed at the A₂ peak, with a signal-to-background ratio of greater than 1:1. A single D-wave Breit-Wigner distribution with a quadratic background gives a good fit to the data, yielding the parameters M₀=(1.324±0.003) GeV/c² and Γ₀=(0.104±0.009) GeV/c². The spectrum is incompatible with a dipole shape.     

Investigation of the HFS in the 6s6p1P1 state of 173Yb(I) LC and AC spectroscopy

The hfs of the 6¹P₁ state of ¹⁷³Yb has been investigated by level-crossing and anticrossing spectroscopy. From an optimal fit of experimental and calculated signal curves we get the hfs coupling constants: A = 58.45(80) MHz, B = 589.6(13.0) MHz.     

Optical pumping of short lived Β-radioactive isotopes and the magnetic moment of37K

²¹Na (T _1/2=23 sec) and³⁷K(T _1/2=1.25 sec) have been produced in gas targets by (d, n) reactions and polarized by means of optical pumping or spin exchange scattering with optically pumped⁸⁷Rb. An asymmetry up to 3% in theΒ-decay of the polarized nuclei was found, which served to detect rf transitions between hfs levels of the atomic ground states of²¹Na and³⁷K.δF=0 andδF=1 resonances have been recorded, yielding spin, hfs separation and magnetic moment, especiallyI(³⁷K)=3/2,δW(³⁷K)=240.266 (3) Mc/sec andΜ _I(³⁷K)=0.02033(6) nm (diamagnetically corrected). For²¹Na earlier rf-spectroscopic data have been confirmed.