Measurement of the 50Cr(γ, n)49Cr cross section with monochromatic γ-rays

The ⁵⁰Cr(γ, n)⁴⁹Cr cross section has been measured over the energy range E_γ = 20.43 to E_γ = 22.22 MeV using monochromatic γ-rays from the ³H(p, γ)⁴He reaction and detecting the resulting ⁴⁹Cr positon activity. The γ-rays were monitored by a 12.7 cm × 15.2 cm NaI(Tl) crystal. The positon activity was determined by a coincidence detector consisting of two 7.62 cm × 7.62 cm NaI(Tl) crystals set on the annihilation radiation photopeaks. The γ-ray energy resolution was less than 110 keV over the whole energy range. Structure in the cross section was not observed.     

The levels of144Pr from the decay of144Ce

The level scheme of¹⁴⁴Pr has been studied from the decay of¹⁴⁴Ce. The intensities and energies of gamma rays have been determined with a X-ray Ge(Li) detector. TheK-shell internal conversion coefficients for γ-rays have been measured with theK X-ray/γ-ray ratio method using NaI(Tl)—X-ray Ge(Li) coincidence techniques.     

Investigation of the reaction Dy164 (n, γ) Dy165

The level structure of Dy¹⁶⁵ has been investigated at the Karlsruhe research reactor using thermal neutron capture in Dy¹⁶⁴. The target was Dy₂O₃ enriched to 92.71% Dy¹⁶⁴. Neutrons were either monochromized by Bragg reflection from a lead crystal or transmitted through a bismuth single crystal filter. High-resolution measurements of the capture spectrum have been performed by means of a Ge(Li) 5-detector pair spectrometer and a Ge(Li) anti-Compton assembly. A large number of new lines has been observed. Cascade relationships were studied by using several techniques: a double coincidence apparatus with 4″ Ø×5″ NaI(Tl) detectors, a coincidence system containing a scintillation detector and a 34 cm³ Ge(Li)-diode as well as a two-parameter system involving the pair spectrometer (with NaI (Tl) as the primary detector) and a single 4″Ø×6″ NaI (Tl) counter. In the framework ofNilsson's model and simple microscopic pictures of vibrational states the results are consistent with the following spectroscopic interpretation: 0 keV, 7/2⁺[633]; 108.2 keV, 1/2^?[521]; 184.3 keV, 5/2″[512]; 533.5 keV, 5/2″ [523]; 538.6 keV, 7/2⁺[633] +Q₂₂; 570.3 keV, 5/2^?[512]+Q₂₂+1/2^?[510]; 573.6 keV, 3/2^? [521]+1/2^?[521]+Q₂₂; 1103.3 keV, 1/2^? [521]+Q₂₂+3/2^? [521]. For comparison preliminary results are given for the isotonic nucleus Yb¹⁶⁹.     

The decay of 31Ga34

Ge(Li) single γ-ray measurements and a NaI(Tl)Ge(Li) coincidence experiment were performed in a reinvestigation of the decay of 15 min ⁶⁵Ga. Eighty-nine γ-rays were attributed to this decay. In the proposed decay scheme 32 of these γ-rays (representing about 99.5 % of the total intensity of the γ-rays) were placed. The intensity of the annihilation radiation was determined using also a mass-separated source.     

The decay of Ag

The γ-radiation following the decay of ¹¹²Ag has been studied with a Ge(Li) detector. A total of 76 γ-rays was observed. The γ-γ coincidence and angular correlation relations involving the 617 keV 2⁺-0⁺ transition have been measured using Ge(Li)-NaI(Tl) and NaI(Tl)-NaI(Tl) detectors. These results have been used to confirm spins and parities of some levels of ¹¹²Cd in the proposed decay scheme. Cross sections for ¹¹²Ag production by ¹¹⁵In(n,α) and ¹¹²Cd(n, p) reactions have been measured; the ¹¹²Ag half-life has been determined as 3.14 ± 0.02 h.     

The decay of 44Sc

The 3.9 h decay of the ⁴⁴Sc ground state has been investigated with a ⁴⁴Ti source. In a singles experiment with a Ge(Li) detector and a γ-γ coincidence experiment with a NaI(Tl)-Ge(Li) detector arrangement a (0.010 ± 0.002)% EC branch to the 3.30 MeV level of ⁴⁴Ca has been found. The γ-decay branching ratio of the 3.30 MeV level has been determined.     

Chemical states of57Fe-atoms after ec-decay of57Co-labelled Co(BrO3)2·6H2O studied by coincidence Mössbauer spectroscopy

Two kinds of time differential Mössbauer spectra of⁵⁷Co-labelled Co(BrO₃)₂·6H₂O were measured at room temperature by delayed coincidence technique, i.e., one was the delayed coincidence between 122 keV γ ray and 14.4 keV γ ray (γ, γ-ray coincidence), and another was the coincidence between 6.3 keV KX ray and 14.4 keV γ ray (X, γ-ray coincidence). The time dependence of chemical states of⁵⁷Fe-species were observed on γ, γ-ray and X, γ-ray coincidence Mössbauer spectra. The relative area intensities of⁵⁷Fe(II) observed on the X, γ-ray coincidence spectra were larger than those on the γ, γ-ray coincidence spectra on every time windows.     

Low-lying 134Cs excited states from the (n, γ) reaction

Low-energy γ-ray and conversion electron spectra from the ¹³³Cs(n,γ)¹³⁴Cs reaction have been investigated with a bent cyrstal spectrometer, β-speetrometer, Ge(Li) and Si(Li) detectors. Gamma-gamma coincidence measurements were made with the Ge(Li)-Ge(Li) arrangement. Gamma-gamma delayed coincidences have been studied with the use of the Ge(Li)-NaI(Tl) coincidence set-up. The decay of 2.9 h ^134mCs has been investigated with the prism β-spectrometer and Ge(Li) detector. The half-lives of the 176.403 and 257.112 keV levels have been measured to be 49.7 ± 0.8ns and 12.3 ± 1.1 ns respectively. The neutron binding energy B_n have been calculated to be 6891.4 ± 1.3 keV. Spin and parity assignments have been made for almost all the levels. The possible structure of the levels deduced is discussed.     

The electron capture decay of 85gsr

In order to resolve the controversy concerning the existence of an 868 keV γ-transition in the decay of 65d ^85sSr and to determine the electron capture decay energy, radiochemically separated sources, Ge(Li), Ge(Li)-NaI(Tl), and NaI(Tl)-NaI(Tl) spectrometers have been used for singles and (X-ray-γ and γ-γ coincidence measurements. A γ-ray at 868.5±0.5 keV decaying with a 65±5 d half-life was conclusively identified in ^85gSr decay. From measurements of the ratio $\text{P}{}_{\mathrm{\kappa (868.5)}}\text{P}{}_{\mathrm{\kappa (514)}}$ of K-capture probabilities by (KX-ray-γ coincidences, a value of Q_EC was determined for the EC decay feeding the 868.5 keV transition. Thus, a level in ⁸⁵Rb is established at 868.5 keV, and an upper limit of 0.45 μsec is set on its lifetime.     

用低能弱γ源测量电子对的近阈产生截面

用2.7μCi的⁶⁰Co弱γ源和NaI(Tl)与Ge(Li)双探测器符合测量方法,测量了Al,Zn,Sn,Pb四种样品的电子对产生绝对截面。测量结果与前人用很强γ源得到的结果相符合,并验证了在近阈条件下,对产生截面满足Jaeger关系式:σ_pair=(Z²+aZ⁴)σ₀,求得对⁶⁰Co源γ光子,α=(1.51±0.23)×10^-4,σ_{0关键词：}     

Projectile-like fragments excitation and gamma-rays emission after the deep inelastic reaction of32S on58Ni

The deep-inelastic reaction induced by 143 MeV³²S on⁵⁸Ni have been studied detecting projectile-like fragments (PLF) in coincidence withγ-rays in NaI(TI) scintillators. γ-ray multiplicity and anisotropy have been derived for Z_plf=14, 15 as a function of energy loss and/or γ-energy. The information obtained are compared with a discrete γ-line study of the same reaction. The effect of the exit channel selection (ejectileZ, energy loss,E _γ) on the γ-observables is discussed in connection with the evidence of a strong PLF γ-emission.     

The beta branching ratio and conversion coefficients in the137Cs decay

The decay of¹³⁷Cs has been reinvestigated using several precision counting methods. The emission rate ofβ-particles plus internal conversion electrons was measured by the 4π-proportional counter method using vacuum evaporated sources free of self-absorption and checked by the liquid scintillation method. TheK-conversion coefficient was determined by the electron X-ray coincidence method using a magnetic spectrometer and a high resolution Si(Li) detector. TheK/(L+M+...) conversion ratio and a second less accurate value for the β-branching ratio were obtained from the recorded electron spectra. Theγ-ray emission rate of all sources was determined to within ±0.14%, on the average, with a calibrated NaI(Tl) crystal detector. As results the intensity of theβ-decay to the ground state of¹³⁷Ba could be determined to (5.4±0.3)% of the¹³⁷Cs decays, theK-conversion coefficient to 0.0916±0.0004, and theK/(L+M+...) conversion ratio to 4.41±0.04. From these values the γ-ray emission intensity is (85.1±0.4)% of the¹³⁷Cs decays and theK X-ray emission intensity is (8.13±0.10)% of the emittedγ-rays. All errors are discussed in detail.     

High-spin states in 222Th

Levels to spin 16⁺ in the ground band and 17^? in the octupole band in ²²²Th have been identified using the reaction ²⁰⁸Pb(¹⁸O, 4n)²²²Th at 93 MeV. To suppress intense γ-ray background from fission a residue detector was built and operated in coincidence with the Ge(Li) and NaI(Tl) detectors. The apparent moment of inertia in the ground-state rotational band rises very rapidly with increasing spin, however, no indications of backbending were observed. The octupole band at low spin has an aligned angular momentum $\text{J ≈ 3}\text{h}\text{?}$ relative to the ground-state band. Strong cross-band E1 transitions competed with collective E2 transitions within each band. Analysis showed that the ratios $\text{B(}\text{E}\text{1)}\text{B(}\text{E}\text{2)}$ were within experimental uncertainty independent of both the spin and parity of the parent state.The average γ-ray multiplicity per cascade was measured for ²²²Th. The results were in reasonable agreement with the computer code ORNL-ALICE.     

The decay of115 mIn

The decay of^115m In has been investigated using accurate counting methods. The emission rate of conversion electrons plusβ ^?-particles was determined with a 4π proportional flow counter. The total andK-shell internal conversion coefficients of the 336 keVγ-ray in¹¹⁵In were measured by the electron X-ray coincidence method using combinations of a Si surface barrier with a NaI(Tl) detector and of a magneticβ-spectrometer with a high energy resolution Si(Li) detector, respectively. The conversion ratioR=K/(L+M+...) was deduced from electron spectra recorded with the magneticβ-spectrometer. The 336 keVγ-ray emission rate of all used sources was determined with a calibrated NaI(Tl)γ-ray spectrometer. A Ge(Li) detector has been used to determine the relative intensity of the 497 keVγ-ray in¹¹⁵Sn. As results have been deduced the 336 keVγ-ray emission per decay (N _γ1/N ₀=(45.9 ± 0.1)%), the total internal conversion coefficient (α=1.073 ± 0.014), theK-shell internal conversion coefficient (α _K=0.843±0.012), the conversion ratioR=3.63±0.07, theβ ^?-transition per decay going to the ground state (N _β1/N ₀=(5.0 ± 0.7)%) and to the first excited level in¹¹⁵Sn¹¹⁵Sn(N _β2/N ₀=(0.047 ± 0.002)%), and the 497 keVγ-ray emission (N _γ2/N _γ1=(0.103 ± 0.004)%). From the obtained internal conversion data it follows that the 336 keVγ-ray transition is ofM4 character with anE5 admixture of less than (3.5±1.5)%. The half-life of the isomeric state¹¹⁵ mIn has been determined with four different methods. The result isT _1/2=(4.486±0.004) h.     

The lifetime of the 266 keV level in 206Tl

The lifetime of the ²⁰⁶Tl 2^? state at 266 keV has been measured by the delayed coincidence technique. The state was populated via the γ-decay of high-lying states excited in the ²⁰⁵Tl (d, p)²⁰⁶Tl reaction at E_d = 9.0 MeV. Delayed coincidences between a Si surface-barrier detector and a Ge(Li) detector resulted in a mean life for the 266 keV level of τ = 3.3(2) ns. The deduced B(E2) value of 171 (11) e² · fm⁴ indicates strong configuration mixing of two-hole states in this level.     

A multi NaI(Tl) detector array for medium energyγ-ray spectroscopy

An array of seven hexagonal NaI(Tl) detectors has been set up for measuringγ-ray spectra in the energy region 5 MeV ≤E _γ ≤ 40 MeV with good accuracy. This is in contrast to earlier set ups which mostly used one large sized (about 10 inchesφ × 15 inches long)NaI(Tl) detector. This set up has been made for the study ofγ decay of GDR based on high spin states and ultra-dipole radiations. The array has been provided with the following features: a) TOF discrimination against neutrons, b) pile up detection and elimination, c) active and passive shielding to cut down background and d) an array of trigger counters for multiplicity dependence measurements. The well known program EGS4 has been used to determine the response of the array forγ-rays in the energy region 5–40 MeV and several test measurements have been carried out to confirm the validity of the calculated response functions. Some typicalγ-ray spectra fromα and¹⁶O induced reactions measured at VECC, Calcutta and Pelletron accelerator at TIFR are also shown.     

The decay scheme of 127Ba and half-lives of some low-lying excited states in 123, 125, 127, 129Cs

Radioactive sources of ^{123, 125, 127, 129}Ba obtained in the spallation reaction have been studied with Ge(Li), Si(Li), NaI(Tl) and plastic detectors. On the basis of γ-ray energies, intensities, energy sums and coincidence information, the decay scheme has been proposed for ¹²⁷Ba. No high-spin isomer of ¹²⁷Ba has been observed. The lifetimes of $\text{5}\text{2}$⁺ → $\text{1}\text{2}$⁺ transitions in ^{123, 125, 127, 129}Cs have been measured. No evidence for the shape isomerism in ¹²⁷Cs has been found.     

Accurate determination of the half-lives of95Zr and95Nb

The half-lives of⁹⁵Zr and⁹⁵Nb have been determined byγ-ray counting using a Ge(Li) detector and a NaI(Tl) crystal. Data have been recorded at regular time intervals during time periods up to nine times the respective half-life. The obtained results are T_1/2(⁹⁵Zr)= (64.05±0.06) days and T_1/2(⁹⁵Nb)=(34.97±0.03) days. A detailed discussion of the measurements and the uncertainty assignment is given.     

Study of the high-energy part of the spectrum of γ rays from the neutron-induced fission reaction of 235U nuclei

The spectrum of γ rays from the neutron-induced fission reaction of ²³⁵U nuclei has been investigated in the energy range 10–90 MeV. The experiment was performed in the horizontal channel of a nuclear reactor. The energy spectra was measured using a single-crystal NaI(Tl) spectrometer. The data on the energy dependence of the yield of γ rays have been obtained in the energy range 10–36 MeV. The upper limit of the probability of γ-ray emission has been determined for the range 36–90 MeV.     

Etude du noyau 63Cu par la reaction 60Ni(α, pγ)63Cu

The level structure and the decay properties of low-lying levels in ⁶³Cu have been investigated via the ⁶⁰Ni(α, pγ)⁶³Cu reaction at E_α = 11.7MeV. Using a Ge(Li) detector, the correlations of twenty-five primary γ-rays in coincidence with protons, stopped in an annular detector at approximatively 180° with respect to the beam direction, were measured. From these measurements, branching ratios, γ-ray mixing ratios and spin assignments have been obtained for most of the levels up to 2.4 MeV excitation.