Observation of proton emission following thermal neutron capture in 34.5 d 84Rb

Using a target prepared by on-line isotope separation, thermal neutron capture in ⁸⁴Rb (I^π = 2^?) has been shown to induce proton emission to the ground state (0⁺) and first excited state (2⁺) of ⁸⁴Kr. The branching ratio was measured as $\text{Γ}{}_{\mathrm{<mtext>p</mtext>}}\text{(0}{}^{\mathrm{+}}\text{)}\text{Γ}{}_{\mathrm{<mtext>p</mtext>}}\text{(2}{}^{\mathrm{+}}\text{)}\text{= 4.7 ± 0.7}$, favouring a $\text{3}\text{2}{}^{\mathrm{?}}$ assignment of the capturing state without excluding $\text{5}\text{2}{}^{\mathrm{?}}$, and the (n_th, p) cross section as 12 ± 2 b. The energy available for the process was determined to be 3.45 ± 0.01 MeV, in agreement with other mass data in the region.     

Nuclear orientation study of the excited states of 129I populated in the decay of 129gTe and 129mTe

From the angular distributions of γ-rays emitted by oriented ^129gTe and ^129mTe nuclei implanted in iron by isotope separator, unique spin assignments could be made for the excited states of ¹²⁹I at 487.4 keV $\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{)}$, 696.0 keV $\text{(}\text{11}\text{2}{}^{\mathrm{+}}\text{)}$, 729.6 keV $\text{(}\text{9}\text{2}{}^{\mathrm{+}}\text{)}$, 768.9 keV $\text{(}\text{7}\text{2}{}^{\mathrm{+}}\text{)}$, 1050.4 keV $\text{(}\text{7}\text{2}{}^{\mathrm{+}}\text{)}$ and 1111.8 keV $\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{)}$. In addition, E2/M1 amplitude ratios for the following ¹²⁹I γ-rays (energies are in keV) are derived: δ(459.6) = ?(0.076^+0.037_?0.148); δ(487.4) = 0.50^+0.17_?0.10 or δ^? = 0.35^+0.15_?0.09; δ(556.7) = 0.06±0.02 or δ^? = ?(0.10±0.02); δ(624.4) = 0.10±0.26 or δ^? > 0.4; the 696.0 keV γ-ray is pure E2; δ(729.6) = ?(0.34±0.06) or δ^?1 = 0.55±0.05; δ(741.1) = ?(0.27±0.10) or δ^?1 = ?(0.43±0.12); δ(817.2) = 0.46±0.04 or δ^?1 =0.20±0.03 if $\text{I}{}^{\mathrm{\pi }}\text{(845}\text{keV}\text{) =}\text{7}\text{2}{}^{\mathrm{+}}$; δ(1022.6) = ?(0.02 ±0.02) or δ^?1 = ?(0.23±0.02); $\text{δ(1084) = 0.56}{}^{\mathrm{+0.04}}{}_{\mathrm{?0.14}}$; δ(1111.8) = 0.06±0.05 or δ^?1 = ?(0.08±0.05). The anisotropy of the 531.8 keV γ-ray excludes $\text{1}\text{2}{}^{\mathrm{+}}$ as a possible spin assignment for the 559.6 keV level, so that no $\text{1}\text{2}{}^{\mathrm{+}}$ level is fed in the decay from ¹²⁹Te. Anisotropies for the 209, 250.7, 278.4 and 281.1 keV γ-rays are also measured. Comparison of the level scheme is made with theoretical predictions from both the pairing-plus-quadrupole model and the intermediate coupling unified model.     

SU(6) × SL(3, R) color quark model

A nonrelativistic color quark model based on the spectrum generating group SU(6)×SL(3, R) is presented. The model unifies SU(6) and the Regge classification with linear L vs m² mass spectrum. Baryons are predicted to belong to the ($\text{56}\text{, L}{}^{\mathrm{P}}\text{= (}\text{even}{}^{\mathrm{+}}\text{)}\text{and}\text{(}\text{70}\text{, L}{}^{\mathrm{P}}\text{= (}\text{odd}{}^{\mathrm{?}}\text{)}$ multiplets of the SU (6) × O(3) group.     

Differential cross section zeros for the process NN → ππ

We describe a method for examining the differential cross section zeros for the process spin $\text{(}\text{1}\text{2}\text{+}\text{1}\text{2}\text{) →}\text{spin}\text{(0 + 0)}$. This is illustrated using the reaction $\text{p}\text{p}\text{→ π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$, where three dominant meson spin states are shown to exist in the mass range 2020 to 2580 MeV/c².     

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.     

Investigation of rare non-strange decay modes of the f meson in Π+p interactions at 5GeVc

Rare decay modes of the f meson are studied in the final states Δ⁺⁺π⁺π^?π⁺π^?, Δ⁺⁺π⁺π^?MM and Δ⁺⁺π⁺π^?π⁺π^?MM. The ratio $\text{Γ (f → π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{π}{}^0\text{π}{}^0\text{)}\text{Γ(f → π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$ is 0.23 ± 0.09 and Γ(f → 4 π) saturates the f inelasticity. A 2 s.d. upper limit of 0.09 is found for the branching ratio $\text{(f → ηη)}\text{(f → 2π)}$.     

On the continuity of generalized eigenfunctions of the Schrödinger operator

We prove that the generalized eigenfunctions of the Schrödinger operator are continuous for potentials obeing the following assumptions: V=V⁺?V^?,V^±≥0,$\text{V}{}^{\mathrm{+}}\text{∈L}{}^{\mathrm{p}}{}_{\mathrm{<mtext>loc</mtext>}}\text{(}\text{R}{}^{\mathrm{l}}\text{)}$, $\text{V}{}^{\mathrm{?}}\text{∈L}{}^{\mathrm{p}}\text{(}\text{R}{}^{\mathrm{l}}\text{)}$,$\text{p >}\text{l}\text{2}$.     

Spin assignments in 63Ni through 62Ni(d,p)63Ni

Angular distributions of vector analyzing power have been measured for the reaction ${}^{62}\text{Ni}\text{(}\text{d, p}\text{)}{}^{63}\text{Ni}$ at a beam energy of 10 MeV. The observed j-dependence of vector analyzing power allows unambiguous spin assignments to be made for the following states in ⁶³Ni (excitation energies in MeV): $\text{0,}\text{1}\text{2}{}^{\mathrm{?}}$; $\text{0.087,}\text{5}\text{2}{}^{\mathrm{?}}$; $\text{0.155,}\text{3}\text{2}{}^{\mathrm{?}}$; $\text{0.515,}\text{3}\text{2}{}^{\mathrm{?}}$; $\text{1.003,}\text{1}\text{2}{}^{\mathrm{?}}$; $\text{2.297,}\text{5}\text{2}{}^{\mathrm{+}}$; $\text{2.700,}\text{1}\text{2}{}^{\mathrm{?}}$; $\text{2.953,}\text{1}\text{2}{}^{\mathrm{+}}$; $\text{3.292,}\text{5}\text{2}{}^{\mathrm{+}}$; $\text{3.932,}\text{5}\text{2}{}^{\mathrm{+}}$; $\text{3.951,}\text{5}\text{2}{}^{\mathrm{+}}$; $\text{4.387,}\text{5}\text{2}{}^{\mathrm{+}}$. An assignment of $\text{9}\text{2}{}^{\mathrm{+}}$ is suggested for the state at 2.519 MeV. The data for the unresolved l_n = 4, 1 doublet (1.294, 1.327) MeV indicate the $\text{3}\text{2}{}^{\mathrm{?}}$ spin assignment for the 1.327 MeV state. The main features for all the data are in agreement with DWBA calculations.     

Gamma decay of particle-core states in 209Pb

A γ-decay scheme for levels in ²⁰⁹Pb up to 4.13 MeV of excitation has been established by means of the reaction ²⁰⁸Pb(d, pγ)²⁰⁹Pb. In high efficiency p-γ coincidence measurements γ-cascades have been observed from the single-particle states and from core-excited states with very small single-particle strength. Assuming a qualitative validity of the weak-coupling model spins and main configurations of particle-core states can be deduced from their γ-decay. The $\text{J}{}^{\mathrm{\pi }}\text{= (}\text{3}\text{2}{}^{\mathrm{?}}\text{,}\text{5}\text{2}{}^{\mathrm{?}}\text{or}\text{7}\text{2}{}^{\mathrm{?}}\text{,}\text{11}\text{2}{}^{\mathrm{?}}\text{,}\text{15}\text{2}{}^{\mathrm{?}}\text{)}$ members of the $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{?3}{}^{\mathrm{?}}$ multiplet could be located. A systematic manner of doublet splitting is found for the lowest states with main configuration $\text{(}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?1}}\text{?3}{}^{210}\text{Pb}\text{(0}{}^{\mathrm{+}}\text{, 2}{}^{\mathrm{+}}\text{, 4}{}^{\mathrm{+}}\text{, 6}{}^{\mathrm{+}}\text{, 8}{}^{\mathrm{+}}\text{)}$. A new decay branch of the $\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ single-particle state is attributed to an admixture of quadrupole core vibration.     

High spin states in 57Co

High spin states of ⁵⁷Co have been studied via prompt γ-ray spectroscopy in the reactions ⁴⁸Ti(¹²C, p2n) and ⁵⁴Fe(α, p) at 26–48 MeV and 12–24 MeV, respectively. The energies and decay modes of these levels were determined from the analysis of γ-ray singles and γ-γ coincidence spectra, excitation functions, angular distributions and correlations. The relevant lifetimes were measured by the Doppler-shift attenuation method. The new levels established in this work are at 4037, 4814 and 5918 keV with the most probable J^π assignment of $\text{15}\text{2}{}^{\mathrm{?}}$, if $\text{17}\text{2}{}^{\mathrm{?}}$ and $\text{19}\text{2}{}^{\mathrm{?}}$, respectively. The previously known level at 2524 keV was assigned to have $\text{J}{}^{\mathrm{\pi }}\text{=}\text{13}\text{2}{}^{\mathrm{?}}$. These together with the known $\text{9}\text{2}{}^{\mathrm{?}}$(1224 keV) and $\text{11}\text{2}{}^{\mathrm{?}}$(1690 keV) levels constitute the yrast states of ⁵⁷Co. The measured lifetimes of the above six levels are (in order of increasing energies) 0.085±0.030, 0.32±0.10, 0.16±0.06, 0.10_?0.07^+0.06, 1.5_?0.5⁴ and 0.17_?0.07^+0.08 ps, respectively. Comparisons with some theoretical calculations are presented.     

High-spin negative parity states in 19F

Levels at 7.17, 8.29, 8.96 and 9.88 MeV in ¹⁹F have been assigned spin and parity $\text{11}\text{2}{}^{\mathrm{?}}$, $\text{13}\text{2}{}^{\mathrm{?}}$, $\text{11}\text{2}{}^{\mathrm{?}}$ and $\text{11}\text{2}{}^{\mathrm{?}}$, respectively, from resonance strength and γ-ray angular distribution measurements employing the ¹⁵N(α,γ) ¹⁹F reaction. An earlier assignment of $\text{11}\text{2}{}^{\mathrm{+}}$ to the 8.96 MeV level is incorrect. The measured properties of the $\text{11}\text{2}{}^{\mathrm{?}}$ states are compared with the results of both SU (3) shell model and cluster model calculations.     

SIMS,AES, work function and flash desorption measurements of the CO adsorption on NiCu alloy surfaces

The chemisorption of CO on Cu, Ni and CuNi alloy surfaces was examined by SIMS, work function measurements and desorption spectroscopy. Using a dynamic SIMS technique the M⁺, M⁺₂, MCO⁺ and M₂CO⁺ emission at different temperatures (100–400 K) was measured as a function of CO exposure. In agreement with the work function and desorption experiments an increase of M⁺ and MCO⁺ emission due to the CO adsorption on Cu was found only at low temperatures (100–190 K). On the Ni surface an increase of Ni⁺, NiCO⁺ and Ni₂CO⁺ was measured up to 400 K. The adsorption of CO on CuNi alloy surfaces — as derived from the work function measurements — can be described by the assumption of two different states of adsorbed carbon monoxide. They can be characterized by different binding energies and from sign and magnitude different work function changes. These states were interpreted as adsorption at Ni or Cu sites of the alloy surfaces, respectively. To a certain extent the SIMS results from the alloy surfaces are incompatible with the work function measurements and desorption spectroscopy and the SIMS studies on the pure metals. A Cu⁺ emission with comparable intensity to the Ni⁺ emission was found for alloys with bulk concentrations of 60 and 40 at% Cu at 300 K. The ratio $\text{Ni}{}^{\mathrm{+}}\text{Cu}{}^{\mathrm{+}}$ was nearly independent of CO pressure and temperature. The measured ratios of $\text{Cu}{}^{\mathrm{+}}{}_2\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$, $\text{Ni}{}^{\mathrm{+}}{}_2\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$ and $\text{CuNi}{}^{\mathrm{+}}\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$ with values about 10^?2 can be explained the basis of a statistical arrangement of Cu and Ni atoms in the alloy surface. The intensities of the MCO⁺ emissions are 10² times smaller than the corresponding values of the pure metals. No emission of M₂CO⁺ was found on CuNi during CO adsorption.     

Investigation of the low-lying levels of 179Hf with the (n, γ) and (n,e) reactions

The excited levels of ¹⁷⁹Hf are investigated using the thermal neutron capture γ-ray and conversion electron spectra measured with the bent crystal diffraction spectrometer in Risø and the β-spectrograph in Riga. The level scheme contains the odd parity rotational bands $\text{7}\text{2}{}^{\mathrm{?}}\text{[514],}\text{1}\text{2}{}^{\mathrm{?}}\text{[510],}\text{5}\text{2}{}^{\mathrm{?}}\text{[512],}\text{1}\text{2}{}^{\mathrm{?}}\text{[521],}\text{3}\text{2}{}^{\mathrm{?}}\text{[512]}$ and $\text{7}\text{2}{}^{\mathrm{?}}\text{[503]}$. The energies of these levels and the intensity ratios of the transitions between them are calculated taking into account the rotation-particle coupling (RPC). The following even parity levels are proposed: 859.0 and 942.2 keV $\text{(}\text{7}\text{2}{}^{\mathrm{+}}\text{and}\text{9}\text{2}{}^{\mathrm{+}}\text{of the}\text{7}\text{2}{}^{\mathrm{+}}\text{[633]}\text{band}\text{)}$; 1004.1 and 1079.2 keV $\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{and}\text{7}\text{2}{}^{\mathrm{+}}\text{of the}\text{9}\text{2}{}^{\mathrm{+}}\text{[624] + Q(22)}\text{band}\text{)}$; 1186.0, 1199.2 and 1296.4 keV $\text{(}\text{1}\text{2}{}^{\mathrm{+}}\text{,}\text{5}\text{2}{}^{\mathrm{+}}\text{and}\text{3}\text{2}{}^{\mathrm{+}}\text{of the}\text{1}\text{2}{}^{\mathrm{+}}\text{[651]}\text{band}\text{)}$. The levels at 1249.8, 1269.7, 1432.9, 1482.2 and 1755.5 keV, supported by the analysis of the γγ coincidence spectrum and Ge(Li) singles data, are discussed.     

Level structure of 75Se by the 75As(p,nγ)75Se reaction

Excitation functions of γ-rays from the ⁷⁵As(p, n)⁷⁵Se reaction were measured with 2.0 to 3.6 MeV protons to establish the level scheme of ⁷⁵Se up to about 1.5 MeV excitation energy. Internal conversion electrons following the same reaction were measured at 4.5 and 5.0 MeV proton energy. Using theoretical predictions of the statistical compound nucleus model together with deduced internal conversion coefficients, unique spin assignments were obtained for the $\text{112.5(}\text{7}\text{2}{}^{\mathrm{+}}\text{), 427.9(}\text{5}\text{2}{}^{\mathrm{?}}\text{)}$ and $\text{663.9(}\text{5}\text{2}{}^{\mathrm{?}}\text{)}\text{keV}$ levels. Probable spins were proposed to the $\text{286.6 (}\text{3}\text{2}{}^{\mathrm{?}}$ for one of the doublet and $\text{5}\text{2}{}^{\mathrm{?}}$ or $\text{7}\text{2}{}^{\mathrm{?}}$ for the other), 579.4 $\text{(}\text{1}\text{2}{}^{\mathrm{?}}$ or $\text{3}\text{2}{}^{\mathrm{?}}$, $\text{585.8(}\text{9}\text{2}{}^{\mathrm{?}}$ or $\text{11}\text{2}{}^{\mathrm{?}}$ and $\text{747.6 (}\text{5}\text{2}{}^{\mathrm{?}}$ or $\text{7}\text{2}{}^{\mathrm{?}}\text{)}\text{keV}$ levels. Alow-lying $\text{9}\text{2}{}^{\mathrm{+}}$ level was tentatively assigned at 133.2 keV energy. It was found that a low-lying $\text{1}\text{2}{}^{\mathrm{?}}$ level which appears systematically in other odd Se nuclei is absent in ⁷⁵Se.     

Investigation of π−(π+)+4He→π+(π−) + 4n (4p) reactions

The $\text{π}{}^{\mathrm{?}}\text{(π}{}^{\mathrm{+}}\text{) +}{}^4\text{He→π}{}^{\mathrm{+}}\text{(π}{}^{\mathrm{?}}\text{) + 4n (4p)}$ reactions are investigated in the framework of the four-body hyperspherical basis method. It is shown that the effect of the final state interaction between four nucleons is very significant and these nucleons are mainly in the state with total orbital momentum L=0.     

Determination of the isotopic shift of the first resonance line in Cs(I) spectrum for the isotopes 131Cs, 132Cs,and 136Cs

The isotope shifts of the resonance line $\text{λ = 8521}\text{A}\text{?}$ of ¹³¹Cs, ¹³²Cs, and ¹³⁶Cs with respect to ¹³³Cs were determined by a new scanning technique to be $\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{131}\text{Cs}\text{) = +1.70(40)}\text{mK}$, $\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{132}\text{Cs}\text{) = ?0.95(80)}\text{mK}$, $\text{v}\text{?}\text{(}{}^{136}\text{Cs}\text{)-}\text{v}\text{?}\text{(}{}^{133}\text{Cs}\text{) = ?4.0(3.0)}\text{mK}$. In accordance with results from other Cs isotopes and neighbouring elements they show the change 〈δr²〉 in the second radial moment of the nuclear charge distribution to be a factor of 5 to 10 smaller than expected from the model of uniform charge distribution. Integral isotope shifts over the isotopic chains of Xe, Cs, and Ba were analyzed in terms of collective models. Assuming an isotopic shift discrepancy of 0.5 for the nuclear volume shift it was possible to derive deformation parameters $\text{〈β}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ in quantitative agreement with those from B(E2) measurements.     

Nuclear polarization and signs of quadrupole moments of high-spin Gd isomers

Time-differential perturbed-angular-distribution (TDPAD) experiments have been performed on polarized intermediate- and high-spin isomers ${}^{144}\text{Gd}\text{(10}{}^{\mathrm{+}}\text{)}\text{and}{}^{147}\text{Gd}\text{(}\text{13}\text{2}{}^{\mathrm{+}}\text{,}\text{27}\text{2}{}^{\mathrm{?}}\text{,}\text{49}\text{2}{}^{\mathrm{+}}\text{)}$. Excited Gd nuclei populated by $\text{(}{}^{28}\text{Si}\text{, x}\text{n}\text{)}$ reactions were polarized by the tilted-multifoil technique and implanted in a Gd single-crystal host. Observation of the subsequent electric quadrupole interaction with the known electric field gradient yielded negative values of the sign of the deformation for all isomers studied. The magnitude of the induced nuclear polarization P_I was also determined from the TDPAD data and compared to model calculations in order to deduce the average atomic angular momentum and polarization of Gd ions at v/c ～ 0.018.     

Frequency optimized potential energy functions for the ground-state surfaces of HCN and HCP

Potential energy functions for the ground states of the linear triatomics HCN, HNC ($\text{X}\text{?}{}^1\text{Σ}{}^{\mathrm{+}}$) and HCP ($\text{X}\text{?}{}^1\text{Σ}{}^{\mathrm{+}}$) were derived, by minimizing the difference between the observed vibrational frequencies and those calculated from the potentials by a variational method. Good agreement is obtained between the observed and calculated spectra for HCN and HNC. For the HCP system, a secondary minimum is predicted to lie on the ground-state surface (linear HPC) having dimensions $\text{R}{}_{\mathrm{<mtext>HP</mtext>}}\text{= 1.43}\text{A}\text{?}$, $\text{R}{}_{\mathrm{<mtext>CP</mtext>}}\text{= 1.56}\text{A}\text{?}$, and an energy of 3.8 eV above the HCP ($\text{X}\text{?}{}^1\text{Σ}{}^{\mathrm{+}}$) minimum.     

Strong vacuum polarization and self-damping of e+e− annihilation

If the hadronic contribution to vacuum polarization, which is proportional to the ration of e⁺e^? annihilation into hadrons to that into μ⁺μ^? rises asymptotically as a power $\text{β >}\text{1}\text{2}$ of the squared four-momentum, the ratio $\text{σ}\text{(e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→hadrons)}\text{σ}$ point $\text{(}{}^{\mathrm{\sigma }}\text{point =}\text{(4πα}{}^2\text{)}\text{(3s))}$ is bound to be less than $\text{?}\text{(3}\text{tg}\text{πβ)}\text{(8α)}$ and this limit is approached sooner for higher β. Other models of vacuum polarizations are also considered together with their possible origin and implications.