Nuclear moments and optical isotope shifts of108m Ag and110m Ag

The hyperfine structure of the resonance lines of^108m Ag and^110m Ag has been investigated by means of optical interference spectroscopy. The metastable isotopes were produced by neutron irradiation in a reactor. From the measureda- andb-values we derive the value for the nuclear magnetic dipole moment of^108mAgμ _I (108m)=3.577 (20)μ _n and the values for the electric quadrupole momentsQ _I (108m)=1.52(8) bQ _I (110m)=1.65(10) b (without Sternheimer correction). The measured isotope shifts allow the determination of the changes in the mean square charge radii of the nuclei involved:δ 〈r ²〉(108m-107)=0.022(3)fm² δ 〈r ²〉(110m-109)=0.029(2)fm². The isotope positions show odd-even staggering comparable with those of neighbouring isotonic nuclides.     

РАСПАД Ag108m

The -spectrum of the long-living isomer of Ag¹⁰⁸ (T_1/25 years) was studied by means of Ge(Li) semiconductor detectors. Eight gamma transitions were found with energies of 79.5, 405.7, 433.7, 613.5, 633.0, 722.6, 836.5 and 1020 keV and correspanding relative intensities of 0.083, 0.008,1, 1.05, 0.0018,1.02,0.0006 and 0.010. The conversion coefficients and multipolarities were determined for transitions of 79.5, 613.5 and 722.6 keV. In the decay scheme of Ag^108m the sequence of the levels 4⁺ (1047 keV) and 0⁺ (1049 keV) is given and the existence of the levels 1454 keV and 1469 keV is confirmed. Spin and parity 2^– were ascribed to the 80 keV level of Ag¹⁰⁸ on the basis of the multipolarity of the 79.5 keV transition.     

Energieverlustspektren der Alkalihalogenide und der Metalle Cu,Ag und Au und Vergleich mit optischen Messungen

Energy loss spectra of 50 keV electrons have been measured in transmission of the alkali halides and of Cu, Ag, and Au at zero scattering angle. These spectra are compared with the quantity ?Im(1/ε) determined from optical measurements. The general agreement is good, especially in the low energy loss region. In the case that the foil thicknesses could be measured, the absolute intensity of ?Im(1/ε) is found to be equal or up to three times larger than from optical data. In addition to the sharp low energy peaks (excitons), characteristic sharp peaks are found at higher energies: 60 eV for the Li-halides, 33 eV for the Na-halides, and 20 eV, 17 eV, and 13 eV for the K-, Rb-, and Cs-halides respectively. These peaks are very little shifted by the different anions in the crystal lattice and may be due to excitons caused by alkali band transitions. We have further examined several peaks in the loss spectra of LiF, KCl, KBr and the Na-halides: 1. The angular dependence of the loss intensity is in agreement with theory. 2. The dispersion of the peaks is much smaller than for plasma losses. 3. The temperature dependence of the peak energy has been found quite different for different peaks.     

Decay of108, 109, 110Sb

The structure of¹¹⁰Sn is investigated through the decay of¹¹⁰Sb, whose half-life is measured to be 24.0±0.3 s. Gamma ray spectroscopy measurements lead to the construction of a decay scheme comprising 36 transitions among 18 levels in¹¹⁰Sn. Spin and parity of the states involved in the decay are deduced. New isotopes^109,108sb are identified and their decay properties are discussed. The decay half-life of¹⁰⁹Sb is measured to be 18.3±0.5 s and that of¹⁰⁸Sb to be 7.0±0.5 s.     

Copper ion induced reactions on110-108-106Cd,109-107Ag and110Pd. new rhenium,osmium and iridium isotopes

By⁶³Cu induced reactions on¹¹⁰Cd,¹⁰⁸Cd,¹⁰⁶Cd,¹⁰⁹Ag,¹⁰⁷Ag and¹¹⁰Pd targets, new isotopes were searched in the Ir, Os, Re region. Cross bombardments and excitation function measurements were used to identify newα emitting isotopes:¹⁷⁰Ir (E _α = 6.01 ±0.01 MeV?T _1/2=1.1±0.2s),¹⁶⁹Ir (E _α =6.11±0.01 MeV?T _1/2=0.4±0.1 s),¹⁶⁸Ir (E _α =6.22±0.02 MeV,¹⁶⁸Os (E _α =5.66±0.01 MeV?T _1/2=1.9±0.1 s),¹⁶⁷Os (E _α =5.84 ±0.01MeV ?T ^1/2=0.65±0.15s),¹⁶⁶Os (E _α =6.00±0.02 MeV?T _1/2=0.3 ±0.1 s),¹⁶⁵Os (E _α =6.20±0.02 MeV),¹⁶⁹Re (E _α =5.05±0.01 MeV),¹⁶⁸Re (5.26±0.01 MeV?T ^1/2=5.5 ±0.5 s). Theα-decay measurements are compared to theQ _α values obtained from different mass predictions.     

Energieverteilung und Ausbeute der Photo-α-Teilchen aus Al,Ar, Se und Ag

The energy spectra of photoalpha particles from irradiations of natural Al, Ar, Se and Ag with 32.5 MeV bremsstrahlung were measured between 4 and 16 MeV using solid state detectors. Yield values in μb/MeV · ster were found to be 1.3; 3.0; 0.28; and 0.12 for Al, Ar, Se, and Ag, respectively. Simple compound nucleus calculations show qualitative agreement with the measurements.     

Bestimmung der Halbwertszeit von108m Ag über (n, 2n)-Querschnitte des Silbers

The half-life of^108m Ag was determined as (310±132) years by measuring the absolute activity of a sample containing a known number of^108m Ag nuclei. This could be done by evaluating the cross section for the production of the isomerσ ¹⁰⁹Ag(n, 2n)^108mAg=(670±266) mb. From the measured half-life a logft-value of 8.9 for the electron capture decay of the isomer to the 1770 keV state of¹⁰⁸Pd and a transition probability of (1.0±0.4) · 10^?2 Weisskopf units for the M4 transition to the 2^?state of¹⁰⁸Ag were derived. The cross section for thermal neutrons¹⁰⁷Ag(n, γ)^108mAg could be calculated to be (7.5±3.2) b by using a related measurement from the literature.     

High-resolution photoemission from Ag(100), Ag(110), and Ag(111)

Energy distribution curves of photoelectrons emitted normal to (100), (110), and (111) faces of silver have been obtained at photon energies of 21.22, 16.85, and 11.83 eV. The results are compared with Christensen's relativistic band structure calculation of bulk silver yielding a close correspondence between experiment and theory. A surface state in the L gap immediately below the Fermi level is identified.     

ИсслЕДОВАНИЕ γ-ИqZлУЧ ЕНИь Ag110m

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Investigation of Ag^110m -radiation

     

Einfluß der Kristallorientierung auf die Plasmonenintensität in Ag und Si

In energy loss measurements of electrons on monocrystals of silver and silicon in transmission the intensity of the volume plasma loss (Ag 3.8 eV, Si 16.6 eV) is found to be dependent on the crystal orientation. By tilting the crystal relatively to the incident beam (in general some degrees) the intensities of the elastic peak (I _el), the volume plasma peak (I _v) and in Ag additionally that of the surface loss (I _s) at 3.1 eV (damped by a carboncoating) show different variations.I _s in Ag andI _v in thick (>150 nm) Si is as expected proportional toI _el, whereasI _v in Ag and thin Si varies much stronger thanI _el, so that the quotientI _v/I_el is not a constant. Presumably an explanation of this phenomenon lies in the dynamic theory of electron diffraction including inelastic processes.     

Der Zerfall des Ag106g und Ag106m

The decays of the 25 min-Ag^106g and 8.3 d-Ag^106m have been investigated using Ge(Li)- and Si(Li)-counters. Theγ-rays of 17 transitions in the Ag^106g -decay and of 42 transitions in the Ag^106m -decay have been observed and their energies and relative intensities have been determined. The intensities of theseγ-rays and the intensities of conversion-electrons known from earlier measurements allow the determination ofK-conversion-coefficients for 23 transitions. The present data are consistent with a level-scheme of Pd¹⁰⁶ having states at 0, 0⁺; 511.8, 2⁺; 1127.8, 2⁺; 1133.1, 0⁺; 1228.8, 4⁺; 1557.4, 3⁺; 1562, 2⁺; 1702.8, 4⁺; 1931.7, 3, 4⁺; 2002, 0⁺; 2040.4, 3, 4⁺; 2076.8, 3, 4⁺; 2084.2, 3^?; 2305.7, 4^?; 2324, 1, 2⁺; 2350.4, 3, 4⁺; 2365.3, 3, 4⁺; 2529, 1, 2⁺; 2756.3, 5⁺; 2951.3 keV, 5⁺. The level-scheme of Pd¹⁰⁶ is compared with the predictions of the vibrational model for spherical nuclei.     

Theoretical studies of chemisorbed oxygen on Ag(110)

The interaction of an oxygen atom with a 26-atom cluster model of the (110) face of Ag has been investigated with ab initio self-consistent-field and configuration-interaction theory. The SCF results for the bridge site (C_2v) predict $\text{r = 0.3}\text{A}\text{?}$ and ω_e = 327 cm^?1, in good agreement with the available experimental evidence. The calculated binding energy (D_e = 9 kcal/mole) is roughly an order of magnitude too small. The inclusion of electron correlation increases r_e and ω_e only slightly, but should have a dramatic effect on D_e. The ground state corresponds to a “surface oxide” state. The theoretical projected density-of-states curves exhibit “bonding” and “anti-bonding” O(2p) peaks, separated by ~ 6 eV, in good agreement with recent angle-resolved photoemission data.     

Adsorption and reaction of bromine with Ag(110)

The adsorption and reaction of Br₂ with Ag(110) was studied with Auger electron spectroscopy, LEED, work function measurements and thermal desorption spectroscopy in the temperature range of 130–1000 K. Depending on Br coverage and crystal temperature, four different adsorption and reaction states could be detected. For fractional monolayer coverages, chemisorbed Br(ad) is found to be the most stable species. This adsorption state saturates for θ(Br) ? 0.75. In the chemisorption stage, two LEED patterns, a p(2 × 1) with θ(Br) ? 0.5 and a c(4 × 2) with θ(Br) ? 0.75, were observed. For higher Br₂ exposures and T = 130 K a layer-by-layer growth of AgBr is detected. At higher temperature, T > 190 K, there is evidence for a transformation from a 2D growth mechanism of AgBr into a 3D agglomeration of larger AgBr cluster. Molecularly adsorbed.