Decay properties of76m Br

The remeasured half-life of^76m Br was found to be 1.31±0.02s.γ-ray and conversion electron measurements gave for two cascading transition energy values 57.11±0.02 and 45.48±0.02 keV with multipolaritiesM2 and M1, respectively. The 4⁺ isomeric state at 102.59±0.04 keV is placed in the⁷⁶Br level scheme. The intensity of the cross-over transition is less than 0.8% of isomeric decays.     

Deformation in the light Br isotopes

The nuclear ground state spins of the odd-A Br nuclides^{75, 77, 79}Br with Z=35 are all 3/2⁻. Nilsson orbital calculations show that the 35^th proton occupies the f_5/2 [301]3/2⁻ orbital for ε<0.20 and the p_3/2 [312]3/2⁻ orbital at larger deformations. The magnetic moments of these two states differ by a factor of two, giving clear evidence for the magnitude of the ground state deformation. Low Temperature Nuclear Orientation measurements made in Oxford and Bonn on^{76, 77g}BrFe prepared at ISOLDE, and on line at the SERC Daresbury Laboratory on^{72, 74m, 75}BrFe, have yielded the magnetic moments of these isotopes, using a two non-zero field model with magnetic hyperfine fields of +81.38(6) T and 26(2) T. The spin of the⁷³Br ground state is also deduced. An interpretation of the ground state configurations of these isotopes is given.     

Candidate of the member of three-phonon multiplet observed in the β + +EC decay of 76Br

The decay scheme of ⁷⁶Br is established by the ⁷⁶Br(T _1/2?=?16.2 h) β ^?+?/EC study. The 1791.31 keV level, which was identified initially by Müller et al with ⁷⁶Se(p, p ^′) reaction more than three decades ago, is reconfirmed. However, the spin and parity have not been assigned by Müller et al. Now we consider it reasonable to assign the 1791.31 keV level as a new candidate of the three-phonon multiplet in ⁷⁶Se. In addition, in order to study the deformation of ⁷⁶Se which lies in transitional region between strongly deformed and spherical nuclei, we calculate the total Routhian surfaces (TRS) of positive-parity states by cranking shell model formalism.     

Magnetic moments of isomeric levels in the Br-isotopes measured with in-beam NMR-PAC

The γ-ray angular correlation of the 9/2⁺, 37 μs state in⁸¹Br and of the 181 keV, 120 μs state in⁷⁸Br was disturbed by nuclear magnetic resonance. Theg-factors were determined to be ¦g¦=1.297±0.015 for the 37 μs level in⁸¹Br and ¦g¦=1.025±0.003 for the 120 μs state in⁷⁸Br.     

On the magnetization process in an ising-spin lattice

Gamma ray spectra of a mixture of the isotopes⁸⁶Br and⁸⁷Br have been measured by means of a Ge(Li) detector. Both manual and automated techniques were used to separate bromine from other fission products of natural uranium. A total of 13 gamma rays were observed. The most intense of the⁸⁶Br gamma peaks (1,565 keV) was found to grow in with a half-life of 4.5±1 s. This is explained to be due to an isomeric state in⁸⁶Br decaying to the ground state.     

Core excitation in79Br and81Br

TheE2 andM1 reduced transition probabilities between the low lying levels, in the case of⁷⁹Br and⁸¹Br, have been calculated on the core-excitation model. To account for the observed M1 transition probabilities admixture among the like spin states is considered. In addition, the ground state static moments have been computed. For the same amount of admixture among the like spin states, a good agreement with the experimental results is obtained, for both⁷⁹Br and⁸¹Br. The results are compared with other existing theoretical calculations. From our analysis, we obtain, the quadrupole moment of the first excited 2⁺ state in the neighbouring even-even nuclei. It is in good agreement with the value calculated on the basis of the anharmonic vibrational model.     

MRSDCI study on potential energy curves and ro-vibrational spectra of the BBr molecule

Four low-lying electronic states of the BBr molecule, including Σ⁺ symmetry and Π symmetry with singlet and triplet spin multiplicities, have been studied using the complete active space self-consistent-field method followed by multi-reference single and double excitation configuration interaction calculation. For the ground state, four isotopes (¹¹B⁷⁹Br, ¹¹B⁸¹, ¹⁰B⁷⁹Br, ¹⁰B⁸¹Br) of the BBr molecule have been studied, since their experimental spectroscopic constants and ro-vibrational energy levels are abundant. For the three excited states, just the most natural abundance isotope–¹¹B⁷⁹Br–is investigated. The spin–orbital coupling effect for the a³Π state is also considered. Finally, the analytical potential energy functions of these states are fitted except for the ³Σ⁺ state because its potential well is too shallow to be fitted with available functions. These results have been compared in detail with those of the investigations reported in the literature.     

A low-spin isomer in 74Br; Its half-life and decay scheme

The isotope ⁷⁴Br was produced as the daughter of ⁷⁴Kr. This production mode leads to a ⁷⁴Br isomer whose half-life was measured to be 25.3 ± 0.3 min. A decay scheme based on the 85 observed β-delayed γ-rays suggests the spin assignment (0, 1)^?. Previous detailed studies have reported a 41.5 ± 1.5 min, 4^? isomer of ⁷⁴Br which is produced directly in nuclear reactions. There is no indication which of the two isomers represents the ground state of ⁷⁴Br.     

80mBr/80Br – A New Electron-Gamma PAC Probe

Conversion electron-gamma PAC measurements of the 49–37 keV cascade in ⁸⁰Br through the intermediate 2⁻ state with T _1/2=7.4 ns were performed with a system of two magnetic lens spectrometers and two BaF₂ scintillation detectors. The parent ^80mBr activity with a halflife of 4.4 hrs was implanted into Ni, Zn and graphite at the ISOLDE separator at CERN. The observed interaction frequency in the nickel matrix is in good agreement with the known value of the hyperfine field for Br in Ni and the magnetic moment of the 2⁻ state. From the measured quadrupole interaction in Zn and graphite the electric field gradients at Br were obtained. This revised version was published online in September 2006 with corrections to the Cover Date.     

On-line orientation of bromine isotopes

Assignments for the principal Nilsson configuration in light β⁺-decaying bromine isotopes were proposed in a contribution to the OLNO-1 conference. These assignments were made on the basis of magnetic moments derived from the temperature dependence of anisotropies in daughter Se isotopes observed in the DOLIS-COLD facility at Daresbury. Anisotropy measurements have since been extended to a lower base temperature in^74m Br and^72g Br decay, leading to more stringent limits on the ground state moment of⁷²Br. The proposed π[312]3/2 configuration for⁷⁵Br has also now been confirmed by a measurement of the sign of its magnetic moment. This was done by observing the β-asymmetry in⁷⁵Br decay using high purity Si detectors mounted within the dilution refrigerator.     

Decay properties of neutron deficient Kr isotopes

The decay properties of the neutron deficient isotopes^73–77Kr and^73–76Br have been studied at the ISOLDE facility at CERN. The total decay energiesQ, as determined fromβ ⁺ singles orβ ⁺ -γ coincidence measurements, are compared with mass formulae.     

Millimeter-wave spectrum of BrCN produced by dc discharge

Ground state (v=0) and first excited state (v=1) millimeter-wave rotational absorption spectra of cyanogen bromide (BrCN) and some of its isotopic species, have been investigated in the frequency region: 40.0-75.0 GHz using a source-modulated millimeter-wave spectrometer. Millimeter-wave radiation has been produced using a frequency multiplier, the fundamental radiation source being klystrons. BrCN has been produced by applying a dc glow discharge through a mixture of 3-bromobenzonitrile and trifluoromethylbromide (CF₃Br) at low pressure. The quadrupole hyperfine structure of ⁸¹Br and ⁷⁹Br have been resolved, measured, and analyzed. Finally, internuclear distances of BrCN have been determined.     

The β+-electron capture decay of 73Kr

The β⁺– electron capture decay of ⁷³Kr, produced at the ISOLDE CERN facility, has been studied by β-delayed proton and gamma emission. The established decay scheme involves 15 up to now unreported gamma emitting levels in ⁷³Br. The total proton branching ratio has been measured to be 0.0025 ± 0.0003. From this work, a spin and parity 3/2⁻ is assigned to the ⁷³Kr ground state, on the basis of the allowed β branch to the ⁷³Br J^π= 1/2⁻ ground state and the feeding of the 5/2⁺ level located at 286 keV in ⁷³Br. Received: 17 September 1998 / Revised version: 25 January 1999     

Laser spectroscopy of YBr: rotational analysis of the B1Π—X1Σ system

The (ν,0) bands, for ν = 0–5, of the B¹Π-X¹Σ transition of YBr between 806.2–891.2 nm have been studied using the technique of laser vaporization/reaction with supersonic cooling and laser-induced fluorescence spectroscopy. Spectra of both the Y⁷⁹Br and Y⁸¹ Br isotopic molecules were observed and analysed. A least-squares fit of all the measured line positions yielded vibrational and rotational constants for the B¹Π state. The equilibrium bond length of the B¹Π state is determined to be 2.622 5(2) Å.     

225∽260 nm波段溴化氰光解动力学系统性研究

本文报道了在自行搭建的时间切片离子速度成像装置上进行的225∽260 nm波段内溴化氰光解动力学的研究. 在该波段内选取了若干溴原子(²P_3/2或²P_1/2)的共振线对产物溴原子的共振电离并采集其切片影像,得到了光解产物的总平动能谱,进而获得了产物氰基的振转态布居等信息. 本文发现了在Br^*通道,产物氰基的内能激发比Br通道低;Br和Br^*通道产物氰基振动的最高布居分别为v=0和1. 另外,还发现对于Br通道,溴化氰分子在长波处与短波处解离时,氰基产物的振转激发差异很大,这揭示了其显著不同的光解动力学.     

Effects of buried high-Z layers on fast electron propagation

Density functional study is performed on the stabilities, aromaticity, infrared spectra, and optical properties of exohedral fullerene derivatives C₇₆X₁₈(X = H, F, Cl, and Br). The bond dissociation energy and energy gap between HOMO and LUMO of C₇₆H₁₈ are larger than those of the isolated C₇₆F₁₈ and C₇₆Cl₁₈, indicating the possibility for synthesising C₇₆H₁₈ from the viewpoint of thermodynamics and kinetics. C₇₆X₁₈(X = H, F, Cl, and Br) show strong aromaticity, suggesting their stabilities are correlative with the conjugation. The tensors of static linear polarisabilities, mean static linear polarisabilities, polarisability anisotropy, and first-order hyperpolarisabilities of C₇₆X₁₈(X = F, Cl, and Br) increase as X goes from F to Br. We rationalise the nonlinear properties by studying the low-energy optical absorption band obtained by employing time-dependent density functional theory.     

Mean life of the 854 keV 02+ state in 74Se and the coexistence model

The mean life of the first excited 0₂⁺ state in ⁷⁴Se, only 219 keV above the first excited 2⁺ state at 635 keV, was measured to be 1.2±0.2 nsec, with delayed coincidence techniques. The 0₂⁺ state was populated by the decay of ⁷⁴Br produced via the ⁶⁰Ni(¹⁶O, pn)⁷⁴Br reaction. The extracted B(E2; 0₂⁺ → 20₁⁺) value is 14±2 s.p.u. which suggests that the 0₂⁺ state is collective. Application of a coexistence model in terms of spherical and deformed shapes is discussed for ⁷⁴Se.     

High-spin excitations of 84 35Br49 and 85 35Br50: Mapping the proton sub-shells towards 78Ni

The ^{84, 85}Br nuclei have been produced as fission fragments in the fusion reaction ¹⁸O + ²⁰⁸Pb at 85MeV bombarding energy and studied with the Euroball IV array. The high-spin states of the odd-odd ⁸⁴Br nucleus have been identified for the first time, the observed structure being built on the known 6^- isomeric state. High-spin states of ⁸⁵Br have been observed up to 5.4MeV excitation energy and spin I ∼ 21/2. From angular correlation analysis, spin values have been assigned to most of the ⁸⁵Br excited states up to 4MeV. None of these excited states has been found to exhibit a delayed decay having T _1/2 > 10ns. All the observed states in ^{84, 85}Br can be described by various proton excitations involving at least the two sub-shells ( πf _5/2 and πp _3/2) located just above the Z = 28 shell closure.