Inclusive K10(890) production in π−p interactions at 16 GeV/c

Inclusive $\text{K}{}^{10}$ production is studied in π^?p interactions at 16 GeV/c with x_? > 0.2. The $\text{K}{}^{10}$ is found to be pre-dominantly centrally produced with cross section $\text{σ(}\text{K}{}^{10}\text{) = (72 ± 12) μb}$ for x_? > 0.2 and compares closely to data on $\text{K}{}^{10}$ production in π⁺p interactions at the same energy.     

Nuclear wave functions and mesonic exchange currents in the weak transition 16O(0+) ↔ 16N(0−)

We show that any deviation from the closed-core hypothesis for ¹⁶O(0⁺, g.s.) may strongly affect the theoretical ratio of the transition probabilities for the two inverse processes: ${}^{16}\text{O(0}{}^{\mathrm{+}}\text{, g.s.}\text{) →}{}^{16}\text{N(O}{}^{\mathrm{?}}\text{, 120 keV}\text{)}$ muon-capture) and ${}^{16}\text{N(0}{}^{\mathrm{?}}\text{, 120 keV}\text{) →}{}^{16}\text{O(0}{}^{\mathrm{+}}\text{, g.s.}\text{)}$ (beta-decay). As a consequence, the possible evidence for exchange currents in this transition must be reexamined. Preliminary calculations do not exclude a still large meson exchange effect.     

Lithium mobility in the layered oxide Li1−xCoO2

The Li⁺-ion chemical diffusion coefficient in the layered oxide Li_0.65CoO₂ has been measured to be $\text{D}\text{?}\text{= 5 × 10}{}^{\mathrm{?12}}$ m² s^?1 by three independent techniques: (1) from the Warburg prefactor, (2) from the transition frequency for semi-infinite to finite diffusion lengths in steady-state ac-impedence measurements and (3) from a modified Tubandt method that uses ac-impedance data to distinguish interfacial and surface-layer resistances from the bulk resistance of the sample. This value and a small increase in D? with (1 ? x) in Li_1?xCoO₂, 0.45 < (1 ? x) < 0.80, compare favorably with the $\text{D}\text{?}\text{= 5}\text{to}\text{7 × 10}{}^{-12}\text{m}{}^2\text{s}{}^{-1}$ obtained by Honders for this system with pulse techniques. A qualitative discussion is presented as to why this composition dependence and why D? for this system is a factor of five larger than that for Li⁺-ion diffusion in Li_xTiS₂.     

The decay of mass-separated 99g,mAg

The decays of neutron-deficient 15 s ⁹⁹Ag and 124 s ^99gAg nuclides have been investigated at the Leuven Isotope Separator on-line facility. Sources were produced by the ⁹²Mo(¹⁴N, 2p5n) and ${}^{\mathrm{<mtext>nat</mtext>}}\text{Zr}\text{(}{}^{14}\text{N}\text{, x}\text{n}\text{)}$ reactions. Positron, conversion electron, X- and γ-ray singles spectra together with γ-γ coincidence measurements have been performed on mass-separated samples. The $\text{1}\text{2}$^? isomeric level in ^{99)Ag decays with a 163.6 keV isomeric transition to a $\text{7}\text{2}$+ level at 342.6 keV. Of the 106 γ-rays observed in the $\text{β}{}^{\mathrm{+}}\text{EC}$ decay of the 99Ag ground state, 68 γ-rays (92 % of the γ-ray intensity) have been placed in a proposed level scheme. The relative variation of the $\text{J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{+}}\text{and}\text{1}\text{2}$?} levels in odd-mass Ag isotopes has been calculated using a residual proton-neutron delta interaction. The occurrence of decoupled bands in the odd Pd isotopes is discussed. Detailed calculations for ⁹⁹Pd have been carried out in the framework of the Nilsson model (strong-coupling wave functions) using a strong Coriolis band mixing. Energy spectra for high-spin states, wave functions and low-lying non-yrast levels (below E_x = 1 MeV) are also discussed.     

High-spin yrast levels of 38Ar

High-spin states of ³⁸Ar have been studied with the ³⁵Cl(α, pγ)³⁸Ar reaction at E_α = 18 MeV and with the ²⁴Mg(¹⁶O, 2pγ)³⁸Ar reaction at $\text{E(}{}^{16}\text{O}\text{) = 38}\text{and}\text{45}\text{MeV}$. The ³⁸Ar level scheme is obtained with the former reaction from a proton-γ coincidence measurement. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization experiments have been performed with a Ge(Li)-Na(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. Unambiguous spin-parity assignments of $\text{J}{}^{\mathrm{\pi }}\text{= 7}{}^{\mathrm{?}}\text{, 7}{}^{\mathrm{+}}\text{, 8}{}^{\mathrm{+}}\text{, 7}{}^{\mathrm{?}}\text{, 9}{}^{\mathrm{?}}\text{and}\text{11}{}^{\mathrm{?}}$to the ³⁸Ar levels at E_x = 7.51, 8.08, 8.57, 8.97, 10.17 and 11.61 MeV, respectively, are obtained. The 8.57 MeV, 8⁺ level has a mean life below 0.8 ps. Excitation energies, branching ratios, multipole mixing ratios and transition strengths are reported. The experimental results are compared with shell-model calculations.     

High-spin states of 39K and 42Ca

High-spin states of ³⁹K and ⁴²Ca have been investigated with the ²⁸Si(¹⁶O, αpγ)³⁹K and ²⁸Si(¹⁶O, 2pγ)⁴²Ca reactions at a beam energy of 45 MeV. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization measurements were performed with a Ge(Li)-NaI(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. High-spin states of ³⁹K at E_x = 7.14,7.78and8.03 and of ⁴²Ca at E_x = 7.75MeV are established. Unambiguous spin-parity assignments of $\text{J}{}^{\mathrm{\pi }}\text{=}\text{11}\text{2}{}^{\mathrm{?}}\text{,}\text{13}\text{2}{}^{\mathrm{?}}\text{,}\text{15}\text{2}{}^{\mathrm{+}}\text{,}\text{15}\text{2}{}^{\mathrm{?}}\text{,}\text{17}\text{2}{}^{\mathrm{+}}\text{and}\text{19}\text{2}{}^{\mathrm{?}}$ to the ³⁹K levels at E_x = 5.35, 5.72, 6.48, 7.14, 7.78 and 8.03 MeV and of 6^?, 7^?, 8^?, 9^? and(8, 10)^? to the ⁴²Ca levels at E_x = 5.49, 6.15, 6.41, 6.55 and 7.37 MeV, respectively, have been obtained. Further spin-parity restrictions, lifetime limits, excitation energies, branching ratios and multipole mixing ratios are reported. Discrepancies with previous J^π assignments are discussed in detail.     

Spin-parity assignments to high-spin states of 41K and 41Ca

Yrast states of ⁴¹K and ⁴¹Ca have been investigated with the ²⁶Mg(¹⁸O, p2nγ)⁴¹K and ²⁶Mg(¹⁸O, 3nγ)⁴¹Ca reactions at a beam energy of 34 MeV. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization measurements were performed with a Ge(Li)-NaI(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. Unambiguous spin-parity assignments of $\text{J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{+}}$, $\text{11}\text{2}{}^{\mathrm{+}}$, $\text{11}\text{2}{}^{\mathrm{?}}$, $\text{13}\text{2}{}^{\mathrm{+}}$, $\text{15}\text{2}{}^{\mathrm{?}}$ and $\text{19}\text{2}{}^{\mathrm{?}}$ to the ⁴¹K levels at E_x = 1.68, 2.53, 2.76, 2.77, 4.27 and 4.98 MeV and of $\text{9}\text{2}{}^{\mathrm{+}}\text{,}\text{11}\text{2}{}^{\mathrm{+}}\text{and}\text{15}\text{2}{}^{\mathrm{+}}$to the ⁴¹Ca levels at E_x = 3.20, 3.37 and 3.83 MeV, respectively, have been obtained. Excitation energies, branching ratios, multipole mixing ratios and transition strengths are reported. The main features of the ⁴¹K and ⁴¹Ca level and decay schemes are reproduced in a 2p-1h and 3p-2h shell-model calculation.     

Half-life of the ground state of 53Co

The half-life of ⁵³Co(g.s.) was measured by observing its positron emission following the ³⁹K.( ¹⁶O, 2n) reaction induced by a chopped ¹⁶O beam. The contributions to the half-life of positrons from competing reaction products were considered. The final spin distribution and the isomeric ratio values for ${}^{\mathrm{53m}}\text{Co}{}^{53}\text{Co(}\text{g.s.}\text{)}$ and ${}^{\mathrm{53m}}\text{Fe}{}^{53}\text{Fe(}\text{g.s.}\text{)}$ were calculated by the spindependent nuclear evaporation model and found to be different, the former much smaller than the latter. The ${}^{\mathrm{53m}}\text{Fe}{}^{53}\text{Fe(}\text{g.s.}\text{)}$ isomeric ratios were measured for ³⁹K.+ ¹⁶O as well as for ⁴⁰C + ¹⁶O reactions and were found to be in agreement with the above theoretical prediction. On the basis of the smallness of the calculated ${}^{\mathrm{53m}}\text{Co}{}^{53}\text{Co(}\text{g.s.}\text{)}$ ratio, the half-life of ⁵³Co(g.s.) was determined to be $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext><mtext>\; =\; 262\; \pm \; 25\; </mtext><mtext>ms</mtext>}}$.     

Magnetic moment of a core-excited isomeric state in 210Po

The g-factor of the core-excited isomeric 13^? state in ²¹⁰Po has been determined to be +0.546 ± 0.012 with the time-differential spin-rotation method in the ²⁰⁸Pb(α, 2n)²¹⁰Po reaction. This value supports the configuration of $\text{[(π}\text{h}{}^2{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)8}{}^{\mathrm{+}}\text{? 5}{}^{\mathrm{?}}\text{(}{}^{208}\text{Pb}\text{)] 13}{}^{\mathrm{?}}$.     

Transverse spin correlation function of the one-dimensional spin-12 XY model

The transverse spin pair correlation function p^x_n=<S^x_mS^x_m+n>=<S^x_mS^x_m+n> is calculated exactly in the thermodynamic limit of the system described by the one-dimensional, isotropic, spin-$\text{1}\text{2}$, XY Hamiltonian

$\text{H=?2J}\text{∑}\text{l=1}\text{N}\text{(S}{}^{\mathrm{x}}{}_{\mathrm{l}}\text{S}{}^{\mathrm{x}}{}_{\mathrm{l+1}}\text{+S}{}^{\mathrm{y}}{}_{\mathrm{l}}\text{S}{}^{\mathrm{y}}{}_{\mathrm{l+1}}\text{)}$

. It is found that at absolute zero temperature (T = 0), the correlation function ρ^x_n for n ≥ 0 is given by

$\text{ρ}{}^{\mathrm{x}}{}_{\mathrm{2p}}\text{=}\text{1}\text{4}\text{2}\text{π}{}^{\mathrm{2p}}\text{Π}\text{j=1}\text{p?1}\text{4j}{}^2\text{4j}{}^2\text{?1}{}^{\mathrm{2p?2j}}\text{if}\text{n=2p}$

,

$\text{ρ}{}^{\mathrm{x}}{}_{\mathrm{2p+1}}\text{=±}\text{1}\text{4}\text{2}\text{π}{}^{\mathrm{2p+1}}\text{Π}\text{j=1}\text{p}\text{4j}{}^2\text{4j}{}^2\text{?1}{}^{\mathrm{2p+2j}}\text{if}\text{n=2p+1}$

, where the plus sign applies when J is positive and the minus sign applies when J is negative. From these the asymptotic behavior as n → ∞ of |?^x_n| at T = 0 is derived to be $\text{|ρ}{}^{\mathrm{x}}{}_{\mathrm{n}}\text{| ～}\text{a}\text{n}$ with a = 0.147088?. For finite temperatures, ρ^x_n is calculated numerically. By using the results for ?^x_n, the transverse inverse correlation length and the wavenumber dependent transverse spin pair correlation function are also calculated exactly.     

Laser magnetic resonance spectrum of BrO (2Π12 ← 2Π32)

Magnetic dipole transitions between the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ components of the ground electronic state of BrO have been detected using the technique of laser magnetic resonance on three CO₂ laser lines between 964 and 970 cm^?1. This is the first direct observation of the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ state in BrO. The spin-orbit splitting parameter, A, is determined to be ?967.9831(2) cm^?1 for ⁷⁹Br¹⁶O and ?967.9981(2) cm^?1 for ⁸¹Br¹⁶O. Accurate values for the rotational constant $\text{B}{}^{\mathrm{<mtext>eff</mtext>}}\text{(}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}$, the hyperfine parameters ($\text{b}{}_{\mathrm{F}}\text{+}\text{2c}\text{3}$) and d, the Λ-doubling parameter p, and the Zeeman parameter g| are also determined from an analysis of the measured spectra.     

A new 5.0 ns isomer in 144Eu

A new 9^? isomeric state having a 5.0 ns half-life has been observed in ¹⁴⁴Eu following the ¹⁴⁴Sm(α, p3n) reactions at 50 MeV. The new isomer most likely has a $\text{(π}\text{g}{}^{\mathrm{?1}}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{v}\text{h}{}^{\mathrm{?1}}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}\text{)}{}_9{}^{\mathrm{?}}$ configuration.     

Polarization spectroscopy of the E0g+-B0u+ band system of Br2

The E-B (0_g⁺-0_u⁺) band system of Br₂ has been investigated at Doppler-limited resolution using polarization labeling spectroscopy. Merged E state data for the three naturally occurring isotopes in the range v_E = 0–16, expressed in terms of the constants for ⁷⁹Br₂, are (in cm^?1) Y_0,0 = 49 777.962(54), Y_1,0 = 150.834(22), Y_2,0 = ?0.4182(28), Y_3,0 = 6.6(11) × 10^?4, Y_0,1 = 4.1876(28) × 10^?2, Y_1,1 = ?1.607(16) × 10^?4, and Y_0,2 = 1.39(39) × 10^?8. The bond distance is $\text{r}{}_{\mathrm{<mtext>e</mtext>}}\text{= 3.194}\text{A}\text{?}$, and the diabatic dissociation energy to $\text{Br}{}^{\mathrm{+}}\text{(}{}^3\text{P}{}_2\text{) +}\text{Br}{}^{\mathrm{?}}\text{(}{}^1\text{S}{}_0\text{)}\text{is 34 700 cm}{}^{\mathrm{?1}}$.     

Investigation of level energies and B(E2) values for rotation-aligned bands in Hg isotopes

High spin states in ^{191, 192, 193, 195, 197, 199}Hg were investigated by observing γ-rays and conversion electrons in the compound reactions ${}^{\mathrm{192,\; 194,\; 198}}\text{Pt(α, x}\text{n}\text{)}\text{and}{}^{192}\text{Pt}\text{(}{}^3\text{He}\text{, 4}\text{n}\text{)}$. In ¹⁹⁷Hg the decoupled band built on the $\text{13}\text{2}{}^{\mathrm{+}}$ state and the semi-decoupled negative-parity band are observed up to $\text{I}{}^{\mathrm{\pi }}\text{=}\text{41}\text{2}{}^{\mathrm{+}}\text{and}\text{33}\text{2}{}^{\mathrm{?}}$, respectively. A careful investigation of ¹⁹⁹Hg revealed no new high spin states above the previously known levels with $\text{I}{}^{\mathrm{\pi }}\text{=}\text{25}\text{2}{}^{\mathrm{+}}\text{and}\text{31}\text{2}$^?. Half-lives were determined for the 10⁺, 7^?, 8^? and 16^? states in ¹⁹²Hg, the if$\text{33}\text{2}{}^{\mathrm{+}}$$\text{states in}{}^{\mathrm{191,193}}\text{Hg and the}$ (frc states in ^{191, 193, 195, 197}Hg. The systematics of the level energies and B(E2) values for the positive-parity ground and $\text{13}\text{2}{}^{\mathrm{+}}$ bands and the negative-parity semi-decoupled bands in ^190–200Hg is discussed.     

High-spin states in 38K

High-spin states in ³⁸K are investigated with the ²⁴Mg(¹⁶O, pnγ)³⁸K reaction at $\text{E(}{}^{16}\text{O}\text{) = 36–44}\text{MeV}$. A recently developed Compton-suppression spectrometer with 120 msr solid angle and a pulsed beam are employed to study their γ-decay. For the E4 transition from the isomeric level at E_x = 3458 keV to the ground state a branching ratio of (0.15 ± 0.02)% is found. On the basis of angular distribution and polarization measurements, in which the delayed feeding component is eliminated, spin-parity assignments are obtained of J^π(2646 keV) = (2, 4)^?, J^π(3420 keV) = (4, 6)^? and J^π(3458 keV) = (5, 7)⁺. Prompt-delayed and prompt γγ coincidence experiments are performed to locate high-spin levels above the isomer. Hitherto unobserved levels of high spin are found at E_x = 5254, 7397, 8693, 8747 and 10980 keV and assignments of J^π = (9⁺), (10^?), (12^?), (11^?) and (13^?) respectively, are suggested by weak-coupling considerations. The experimental results are compared with a large-scale shell-model calculation performed in a configuration space with a ²⁸Si core and ten active particles distributed over the ($\text{2}\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{, 1}\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{, 1}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{, 2}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{)}$ shells. The high-spin states appear to have a rather simple shell-model structure.     

g-Factors of high-spin isomers in 194Hg and 196Hg

The g-factors of the 10⁺ isomeric states in ¹⁹⁴Hg and ¹⁹⁶Hg have been measured using the in beam IPAD method. The results $\text{g(}{}^{194}\text{Hg}\text{) = ?0.24(4)}$ and $\text{g(}{}^{196}\text{Hg}\text{) = ?0.18(9)}$ are in agreement with the value expected for an ($\text{i}{}_1\text{3}\text{2}$^?2) neutron satructure and clearly contradict the previous assignment as ($\text{h}{}_{\mathrm{<mtext>1</mtext><mtext>1</mtext><mtext>2</mtext>}}{}^{\mathrm{?2}}$) proton configurations. Cranking model calculations show that the neutron excitation energies in the rotating frame agree satisfactorily with the experimental energies and that the proton excitations are expected ≈2 MeV above the experimental yrast line     

Charge density wave commensurability in 2H-TaS2 and AgxTaS2

The charge density wave transition in 2H-TaS₂near 75 K has been observed to be incommensurate, using electron diffraction, with $\text{q}{}^1\text{= (}\text{0.338}\text{±}\text{0.002}\text{)a}{}^1{}_0$ along the 〈10.0〉 directions which, within the experimental uncertainty, remains temperature independent to about 14 K. Incommensurate charge density formation is also observed in Ag_xTaS₂ samples for $\text{x?}\text{0.26}$ with an increase in q¹ to $\text{(}\text{0.347}\text{±}\text{0.002}\text{)a}{}^1{}_0$ when x?0.26. Within the experimental error q¹ appears to be temperature independent to 25 K.     

Electron diffraction and infrared study of the semimetallic layered compound Ti1−xVxSe2

The crystals of the system Ti_1?xV_xSe₂ (C ≤ x ≤ 0.05) undergo a second order structural phase transition. Electron diffraction studies show that the transition temperature decreases with progressive V-doping. The phase transition considerably affects the infrared reflectivity, measured at 300 and 77 K in the spectral range 40 cm^?1 to 4000 cm^?1.The presence of free carriers and the existence of optical infrared active E_u phonon modes $\text{(}\text{E}\text{⊥}\text{c}\text{)}$ confer their characteristic appearance to the spectra. At room temperature one phonon structure is measured at 143 cm^?1. At 77 K a new series of phonon peaks appears up to a V-concentration of 5 % as a direct consequence of superlattice formation.At room temperature the plasma-edge shifts towards higher frequencies as the vanadium concentration increases. This effect is caused by a large increase of $\text{N}\text{m}{}^1$, associated with the mixing of impurities. It is indicative of the small density of states at the Fermi level in semimetallic TiSe₂. Our results suggest a phase transition driven by lattice dynamical effects.     

High-spin states in 40K investigated with the 26MG + 16O reaction

Yrast levels in ⁴⁰K and ⁴⁰Ar have been investigated with the ²⁶Mg(¹⁶O, pnγ)⁴⁰K and ²⁶Mg(¹⁶O, 2pγ)⁴⁰Ar reactions at a beam energy of 34 MeV. Gamma-ray angular distribution and γ-γ coincidence measurements have been performed with a high-resolution large volume Ge(Li)-NaI(Tl) Compton-suppression spectrometer. Gamma-ray linear polarizations have been measured with a three-crystal Ge(Li) Compton polarimeter. The ⁴⁰K decay scheme involves new high-spin levels at E_tx = 4365.6±0.3, 4875.6±0.4 and 6227.0±0.5 keV with lifetime limits of < 1, < 1 and < 2ps, respectively. Unambiguous spin-parity assignments of $\text{J}{}^{\mathrm{\pi }}\text{= 5}{}^{\mathrm{?}}\text{, 6}{}^{\mathrm{+}}\text{, 8}{}^{\mathrm{+}}\text{, 9}{}^{\mathrm{+}}\text{and}\text{(8, 10)}{}^{\mathrm{?}}$ to the ⁴⁰K levels at E_x = 0.89, 2.88, 4.37, 4.88 and 6.23 and of $\text{J}{}^{\mathrm{\pi }}\text{= 4}{}^{\mathrm{+}}\text{and}\text{6}{}^{\mathrm{+}}\text{to the}{}^{40}\text{Ar}$ levels at E_x = 2.89 and 3.46 MeV, respectively, have been obtained. Branching ratios and multipole mixing ratios are reported.     

The 5T2g → 5Eg absorption in MgO: Fe2+

At helium temperatures two sharp lines at 9350 and 9510 cm^?1 have been observed for the first tune on the low-energy side of the broad double-peaked absorption corresponding to the ${}^5\text{T}{}_{\mathrm{2g}}\text{→}{}^5\text{E}{}_{\mathrm{g}}$ transition in Fe²⁺ at the octahedral site in MgO. The lower energy line has a half width of 4 cm^?1; Zeeman measurements show that it is of magnetic dipole origin. The Zeeman spectra are consistent with those expected for a pure electronic transition from the (⁵T_2g)T_2g ground state to the ⁵E_g excited state. The second line, with a halfwidth of ~ 35 cm^?1, a vibrational sideband.