Beta-delayed proton emission from heavy nuclei: (I). The observation of coincidences between protons and γ-rays

Coincidences have been detected between γ-rays and β-delayed protons emitted after the decay of very neutron-deficient nuclei. In the three cases studied the decay proceeds to the ground state with branches to the first excited (2⁺) state of the even daughter nucleus of (58±7) % (¹¹⁵Xe to 709 keV in ¹¹⁴Te), (14±3) % (¹¹⁷Xe to 679 keV in ¹¹⁶Te), and (50±10) % (¹⁸¹Hg to 158 keV in ¹⁸⁰Pt). Upper limits of 2 and 6 % can be placed on the branches to the 4⁺ states of ¹¹⁴Te and ¹⁸⁰Pt. For the cases of ^115,117Xe, coincidences with annihilation radiation were also observed; the measured positon/proton ratio determines the difference Q—B_p, between the energy available for electron capture and the proton separation energy for the daughter. For ¹¹⁵Xe the result is 6.20±0.13 MeV, for ¹¹⁷Xe 4.10±0.20 MeV.     

Investigation of the φ-meson resonance by electron-positron colliding beams

Using the colliding beam machine, VEPP-2, the excitation curve of the ø-meson resonance was investigated in the three main decay modes. The resonance parameters obtained are the width, the total cross-section and the branching ratios. Namely: Γ = (4.67 ± 0.42) MevB(K⁺K⁻) = (54.0 ± 3,4) %σ_o = (3.96 ± 0.35) μBB(K^o_sK^O_L) = (25.7 ±3,0) %B(e⁺e⁻ = (2,81 ± 0.25) × 10⁻⁴B(π⁺π⁻π^o) = (20.3 ± 4,2) %     

The pure rotational Raman spectrum of CS2 in the ground and 010 vibrational states

The pure rotational Raman spectra of CS₂ in the 00⁰0 and 01¹0 vibrational states have been observed using a low power HeNe laser (λ = 6328 Å) and a high resolution plane grating spectrograph. The ΔJ = 2 transitions with J = odd in the 01¹0 state are clearly resolved from the ground state transitions thus allowing the determination of some upper state rotational constants. The molecular constants determined in this work are for the 00⁰0 ground state, B_00⁰0 = 0.10912 ± 0.7 × 10⁻⁵ cm⁻¹, (D_J)_00⁰0 = (0.83 ± 0.18) × 10⁻⁸ cm⁻¹ and for the 01¹0 excited state B_01¹0^c = 0.10935 ± 0.00002 cm⁻¹ and (D_J)_01¹0^c = (1.5 ± 0.6) × 10⁻⁸ cm⁻¹.     

A spark chamber measurement of the reactions π + p → ϱ + p at 15 GeV/c

A new method, using spark chambers, for the study of the reactions π^± + p → ?^± + p is described. The charged pion and both γ rays from the π^± decay are detected. Differential and integrated cross sections σ_π⁺=50 ± 9 μb, σ_π⁻=47 ± 9 μb) for 0.0 ?|t|?1. (GeV/c)² and a laboratory momentum (p_Lab) of 15 GeV/c are presented. The momentum dependence of σ_γ^± is well fitted from 2.7 to 16 GeV/c by σ = Kp_Lab⁻ with n_γ⁺ = 1.80 ± 0.80 and n_γ⁻ = 1.87 ± 0.15.     

EPR and optical study of Mn doped ammonium oxalate monohydrate

Studies on fine and hyperfine structures of paramagnetic resonance spectra in single crystals of Mn²⁺: ammonium oxalate monohydrate are reported. As sufficient numbers of lines were not obtained at room temperature, measurements have been done at liquid nitrogen temperature and at the frequency of X-band. The Mn²⁺ spin Hamiltonian parameters have been evaluated employing a large number of resonant line positions observed for various orientations of the external magnetic field and the surrounding crystalline field has been discussed. The values of the zero field parameters that give good fit to the observed EPR spectra have been evaluated. The values obtained for g, A, B, D, E and a are 2.0002±0.0002, (100±2)×10⁻⁴, (79.5±2)×10⁻⁴, (257±2)×10⁻⁴, (85±2)×10⁻⁴ and (−18±1)×10⁻⁴ cm⁻¹, respectively. The percentage of covalency of the metal-ligand bond is also determined. The optical absorption study has been done at room temperature. The observed bands are assigned as transitions from the ⁶A_1g(S) ground state to various excited quartet levels of Mn²⁺ ion in a cubic crystalline field. The electron repulsion parameters (B and C), the crystal field splitting parameter(Dq) and the Trees correction (α) providing good fit to the observed optical spectra have been estimated and the values obtained for the parameters are B=897, C=2144, Dq=910 and α=76 cm⁻¹.     

Single crystal EPR and optical absorption study of Cr doped l-histidine hydrochloride monohydrate

EPR study of the Cr³⁺ ion doped l-histidine hydrochloride monohydrate single crystal is done at room temperature. Two magnetically inequivalent interstitial sites are observed. The hyperfine structure for Cr⁵³ isotope is also obtained. The zero field and spin Hamiltonian parameters are evaluated from the resonance lines obtained at different angular rotations and the parameters are: D=(300±2)×10⁻⁴ cm⁻¹, E=(96±2)×10⁻⁴ cm⁻¹, g_x=1.9108±0.0002, g_y=1.9791±0.0002, g_z=2.0389±0.0002, A_x=(252±2)×10⁻⁴ cm⁻¹, A_y=(254±2)×10⁻⁴ cm⁻¹, A_z=(304±2)×10⁻⁴ cm⁻¹ for site I and D=(300±2)×10⁻⁴ cm⁻¹, E=(96±2)×10⁻⁴ cm⁻¹, g_x=1.8543±0.0002, g_y=1.9897±0.0002, g_z=2.0793±0.0002, A_x=(251±2)×10⁻⁴ cm⁻¹, A_y=(257±2)×10⁻⁴ cm⁻¹, A_z=(309±2)×10⁻⁴ cm⁻¹ for site II, respectively. The optical absorption studies of single crystals are also carried out at room temperature in the wavelength range 195-925 nm. Using EPR and optical data, different bonding parameters are calculated and the nature of bonding in the crystal is discussed. The values of Racah parameters (B and C), crystal field parameter (Dq) and nephelauxetic parameters (h and k) are: B=636, C=3123, Dq=2039 cm⁻¹, h=1.46 and k=0.21, respectively.     

EPR and optical absorption study of Cr-doped ammonium oxalate monohydrate single crystals

The electron paramagnetic resonance (EPR) study of the Cr³⁺-doped ammonium oxalate monohydrate (AOM) single crystal is done at room temperature. Two magnetically inequivalent sites for chromium are observed. The hyperfine structure for Cr⁵³ isotope is also obtained. The spin Hamiltonian parameters are evaluated as: D=(309±2)×10⁻⁴ cm⁻¹, E=(103±2)×10⁻⁴ cm⁻¹, g=1.9820±0.0002, A=(161±2)×10⁻⁴ cm⁻¹ for site I and D=(309±2)×10⁻⁴ cm⁻¹, E=(103±2)×10⁻⁴ cm⁻¹, g=1.9791±0.0002, A=(160±2)×10⁻⁴ cm⁻¹ for site II, respectively. On the basis of EPR data the site symmetry of Cr³⁺ doped single crystal is discussed. The optical absorption spectra are recorded in 195-925 nm wavelength range at room temperature. The energy values of different orbital levels are determined. On the basis of EPR and optical data, the nature of bonding in the crystal is discussed. The values of different parameters are B=803, C=3531, D_q=2208 cm⁻¹, h=0.59 and k=0.21, where B and C are Racah parameters, D_q is crystal field parameter and h and k are nephelauxetic parameters, respectively.     

ππ production by ee annihilation in the ϱ energy range with the Orsay storage ring

A large solid angle detector has been used to observe two body events produced by electron-positron collisions in the Orsay storage ring. From the π⁺π⁻ excitation curve in the ? region we have deduced the amplitude and the phase of the ω-? interference, and the ? resonance paramaters: M_? = (775.4±7.3) MeV, Γ_? = (149.6 ± 23.2) MeV, √B(ω→π⁺π⁻) = 0.19 ± 0.05, φ = (85.7 ± 15.3)⁰, σ(e⁺e⁻→?) = (1.00 ± 0.13) μb at S = M_?², B(?→e⁺e⁻ = (4.1 ± 0.5) × 10⁻⁵, Γ(?→e⁺e⁻) = (6.1 ± 0.7) keV, (g_?²/4π) = 2.26 ± 0.25, (g_?ππ²/4π) = 2.84 ± 0.50.     

Investigation of the Li (e,e′p) reaction at 1200 MeV

The reaction ⁶Li (e, e′p)⁵He has been investigated with a resolution good enough to distinguish the effects of the s- and p-shells of the ⁶Li nucleus. The reaction cross section has been measured as a function of the missing energy from −15 to +30 MeV. The proton angular distribution has been measured at missing energies of 4 and 20 MeV. The comparison of the data with calculations within the framework of the plane-wave impulse approximation gives the harmonic oscillator parameters q_p = 50 ± 5 MeV/c,q_s = 108 ± 9 MeV/c.     

The decays of the Tz = 32 β-delayed proton precursors 83Zr, 87Mo and 91mRu

The decays of the nuclides ⁸³Zr,⁸⁷Mo and ^91mRu have been studied with singles proton counting as well as with pX and pγ coincidences. The half-lives for the three nuclides were measured to be 37.8 ± 1.1 s, 13.3 ± 0.4 s and 7.6 ± 0.8 s, respectively. The proton branch in the decay of ⁸³Zr that populates the first excited state in ⁸²Sr was measured to be (6 ± 4) % of the total delayed proton decay. The corresponding branch in the decay of ⁸⁷Mo, populating the first excited state in ⁸⁶Zr was measured to be (15 ± 8) %. Restrictions to the possible spin and parity assignments of ⁸³Zr and ⁸⁷Mo were deduced from comparisons between the experimental excited-state branches, and those predicted from a statistical model of delayed particle decay. Fits to the endpoints of the delayed proton spectra from ⁸³Zr and ⁸⁷Mo yielded values of the energy available for delayed proton decay (Q_e.c.?B_p) of 2.75 ± 0.10 MeV and 3.7 ± 0.3 MeV, respectively. Comparison between calculated and experimental proton spectra was used as an argument that the source of ⁹¹Ru activity is actually a $\text{1}\text{2}{}^{\mathrm{?}}$ isomer.     

Systematical study of beta delayed proton emission energies

Graphs are given of the maximum proton energies in delayed proton emitters. This quantity, equal to the difference of the electron capture decay energy of the precursor and the separation energy of a proton in the daughter, has been calculated in a least squares adjustment of mass spectroscopic data and nuclear decay and reaction energies. The graphs would lead to expect a 950 keV lower maximum proton energy in⁷³Kr(?p)⁷²Se than has been reported from experiments. They can be used to predict new cases for further studies on this subject.     

Rotationally Resolved LIF Spectra of the AΣ-XΠr Transition of Jet-Cooled GeCl

The A²Σ⁺-X²Π_r band system of ⁷⁴Ge³⁵Cl has been rotationally resolved for the first time using isotopically enriched ⁷⁴GeCl₄ as the precursor in a pulsed discharge jet experiment. The previous vibrational analysis of W. J. Balfour and K. S. Chandrasekhar (1986, J. Phys. B19, L187-L191) has been verified from the observed isotopic splittings of both the chlorine and germanium isotopomers. The ²Π_1/2 components of three vibronic bands have been rotationally analyzed leading to revised values for the ground state rotational constant B″₀=0.154165(35) cm⁻¹ and the lambda-doubling constant p″₀=6.560(97)×10⁻³ cm⁻¹. We have experimentally determined the value of B′_e=0.118710(24) cm⁻¹ for the A²Σ⁺ state leading to an excited state equilibrium bond length of 2.44581(25) Å.     

ESR of Cu doped cadmium (II) formate dihydrate

Electron spin resonance (ESR) of Cu²⁺ doped cadmium formate dihydrate single crystal was studied at room temperature. Copper enters the lattice substitutionally and is trapped at two magnetically inequivalent sites. The observed spectra are fitted to a spin-Hamiltonian of rhombic symmetry with the following values of the spin-Hamiltonian parameters, Cu²⁺(I): g_x=2.097±0.002, g_y=2.1166±0.002, g_z=2.2887±0.002 and A_x=(140±2)×10⁻⁴ cm⁻¹, A_y=(151±2)×10⁻⁴ cm⁻¹, A_z=(239±2)×10⁻⁴ cm⁻¹, Cu²⁺(II): g_x=2.0843±0.002, g_y=2.1045±0.002, g_z=2.2742±0.002 and A_x=(141±2)×10⁻⁴ cm⁻¹, A_y=(158±2)×10⁻⁴ cm⁻¹, A_z=(267±2)×10⁻⁴ cm⁻¹. The ground state wave function of the Cu²⁺ ion in this lattice is evaluated. It is found that the ground state is predominantly |x²−y²〉. The g-factor anisotropy is also calculated and compared with the experimental value. With the help of the optical absorption study, the nature of bonding in the complex has been discussed.     

Decay of kaonium in a chiral approach

The decay of the K⁺K⁻ hadronic atom kaonium is investigated non-perturbatively using meson-meson interaction amplitudes taken from leading order chiral perturbation theory in an approach adapted from that proposed by Oller and Oset (1997) [18]. The Kudryavtsev-Popov eigenvalue equation is solved numerically for the energy shift and decay width due to strong interactions in the 1s state. These calculations introduce a cutoff ∼1.4 GeV in O(4) momentum space that is necessary to regulate divergent loop contributions to the meson-meson scattering amplitudes in the strong-interaction sector. One finds lifetimes of (2.2±0.9)×¹⁰−18 s for the ground state of kaonium.     

Ligand-to-metal charge-transfer quenching of the Eu(D1) state in europium-doped tris(2,2,6,6-tetramethyl-3,5-heptanedionato)gadolinium (III)

Rate constants for the decay of the Eu³⁺(⁵D₁) state in dilute Eu³⁺-doped tris(2,2,6,6-tetramethyl-3,5-heptanedionato)gadolinium(III) are reported for a temperature range 50-315 K. A temperature-independent contribution of 1.3×10⁶ s⁻¹ is attributed to carbonyl mediated ⁵D₁→⁵D₀ relaxation. A temperature-dependent contribution, that has been parameterized as k_CT=Ae^−E_a/kT with E_a=2540±140 cm⁻¹ and A=1.3×10¹² s⁻¹ is attributed to quenching of ⁵D₁ by a low-lying ligand-to-metal charge-transfer state (CTS). The height of the activation barrier, E_a, relative to the previously reported height for charge-transfer quenching of the Eu³⁺(⁵D₀) state in the pure europium analog (J. Phys. Chem. 100 (1996) 9216) is discussed in terms of mechanistic implications. Specifically, these data strongly suggest that quenching of ⁵D₁ by the charge-transfer state is mediated by the ⁵D₀ state with a novel, indirect mechanism.     

Photothermal ionization via excited states of sulfur donor in silicon

Structures in the photoionization cross-section spectra below the extrinsic edge of the doubly charged sulfur donor (613 meV) are attributed to the two-step photothermal excitation process in which the bound electron at the ground state first makes an optical transition to an excited state and it is then thermally released from the excited state to the conduction band. A weak peak (cross-section 7 × 10⁻¹⁹ cm²)at 425 meV is attributed to the intervalley optical transition 1s(A₁)→1s(T₂). Peak observed at 570 meV (10⁻¹⁷ cm²) is attributed to the 1s(A₁→2p₀ intervalley optical transition and the peak at 591 meV (3 × 10⁻¹⁷ cm²) to the 1s(A₁)→2p± intravalley optical transition. Data for electron bound at the neutral gold center has no structures which is consistent with the lack of excited states of a neutral impurity potential.     

Evidence for dipole-quadrupole-octupole mixing in the 902 keV 2 → 2 transition in W

From known conversion coefficients and angular correlations combined with the γ-ray decay deduced from the ¹⁸¹Ta(p, 2n¹⁸⁰W reaction it is found that the 1007 → 104 keV (2⁻ → 2⁺) transition in ¹⁸⁰W has mixing parameters δ₁ = −0.16 ± 0.07 and δ₂ = −0.64 ± 0.17 for M2/E1 and E3/E1, respectively     

EPR and optical absorption studies of Cr ions in potassium sodium dl-tartrate tetrahydrate

EPR spectra of Cr³⁺ ions doped in potassium sodium dl-tartrate tetrahydrate single crystals are recorded at 77 K. The spin Hamiltonian and zero field parameters g, |D| and |E| are measured from the resonance lines obtained at various rotations of the magnetic field. The values obtained are: g_x=1.9257±0.0002, g_y=1.9720±0.0002, g_z=2.0102±0.0002, |D|=313±2 (×10⁻⁴) cm⁻¹ and |E|=101±2 (×10⁻⁴) cm⁻¹. From the results of EPR study, the site symmetry of Cr³⁺ ion in the crystal is discussed. The optical absorption at room temperature is also studied. From the observed band positions, the crystal field splitting parameter (D_q) and the Racah inter-electronic repulsion parameters (B and C) are evaluated. The bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed.     

The semileptonic decay fraction ofB-mesons in the light of interfering amplitudes

Consequences of the interference between spectator amplitudes for the lifetimes and semileptonic decay fractions ofB ⁰ andB ⁺ mesons are discussed. Extracting these amplitudes from a fit to 11 exclusive hadronicB decay fractions we finda ₁=1.05±0.03±0.10,a ₂=+0.227±0.012±0.022, an inclusive semileptonic decay fraction of (11.2±0.5±1.7)%, and a lifetime ratio (B ⁺)/(B ⁰)=0.83±0.01±0.01.Supported under DOE grant number DE-FG02-91-ER40690