B. Nyman

The Level Scheme of 107Cd Studied through the 107Ag (p,nγ) and 106Cd (d, pγ) Reactions and the 107In Decay

The excited levels of 107Cd have been investigated by studying the gamma-rays and internal conversion electrons from the 107Ag(p,n)107Cd and 106Cd(d,p)107Cd reactions and the 107In decay. Based on coincidence measurements, a completely revised 107Cd level scheme including 23 new levels has been constructed. Spins and parities for the levels were deduced from transition multipolarities, log ft-values and the relative excitation functions derived from the reaction measurements. A 1/2- isomeric state (T1/2 = 51.8±2.0 s) at 678.5 keV was identified in 107In.

Decay studies of Au isotopes in the mass number region 186–189

Internal conversion electrons and gamma-rays emitted in the decays of the neutron deficient gold isotopes with mass numbers 186–189 have been studied with a double focussing beta-ray spectrometer and a Ge(Li) detector. Multipolarities for the strongest transitions have been deduced. A revised level scheme for189Pt is proposed. The half-lives of186Au,188Au and189Au are found to be (10.7±0.5), (9.0±0.4) and (28.6±1.0) minutes respectively.

A high-resolution magnetic beta-ray spectrometer adapted for on-line work

Abstract A 50 cm radius iron-yoke double focussing beta-ray spectrometer has been equipped to work on-line at the charged particle beam from an EN Tandem accelerator. The principal features of the experimental arrangements, including target and detector systems, beam transport and focussing and the background shielding are described. Experimental results from on-line internal conversion measurements on different isotopes are presented. On the basis of the experience gained in these measurements some of the possibilities of high-resolution on-line electron spectroscopy are discussed.

IMPROVEMENTS OF A DOUBLE FOCUSSING IRON-CORE SPECTROMETER FOR HIGH RESOLUTION COINCIDENCE AND ANGULAR CORRELATION MEASUREMENTS.

Abstract A 50 cm radius iron-core double focussing beta-ray spectrometer has been equipped with a gamma-ray coincidence arrangement, which can provide measurements of electron-gamma coincidences and angular correlations at high resolution in the electron channel. A special beta-ray spectrometer detector system, employing coincidences between positons and the subsequent annihilation quanta, has been constructed. The natural background of this system is about 1 count/hour, which permits studies of extremely low intensity positon distributions. The isoaberration curves of the beta-ray spectrometer have been measured and from these results optimized shapes of the baffles were constructed. The magnetic field of the spectrometer is measured with a “magnetic stripping” system which is described as is also the automized demagnetization unit.

An internal conversion study of the decay of193Au

The internal conversion spectrum following the decay of193Au has been studied in the electron energy region 0.8 to 700 keV, with the use of high-resolution magnetic beta-ray spectrometers. Several not previously reported transitions have been estabblished. Multipolarities and mixing ratios have been deduced fromK/L and subshell intensity ratios, and the majority of the transitions were found to be ofM1 and/orE2 characters. A revised level scheme for193Pt, which consistently accomodates most transitions, has been constructed. Tentative spin-parity values have been assigned to all levels.

The decay of 192Au

Abstract The 192Pt internal conversion spectrum following the decay of 192Au (5 h) has been studied in great detail by use of a high precision beta-ray spectrometer. The average accuracy of the energy and the relative K-line intensity determinations for the more than 200 established transitions is about two parts in 104 and 10%, respectively. Some tentative gamma-ray intensities are also given. From the end-point energy of the position spectrum, a Q-value of 3514±20 keV for the 192Au decay was obtained. A level scheme comprising 42 excited levels and 140 transitions mainly on the basis of numerical relationships has been constructed.

Techniques for fast evaluation of Ge(Li)-detector gamma-ray spectra with small computers

Abstract A computationally simple technique for evaluating Ge(Li)-detector gamma-ray spectra is described. The energies, intensities and fwhms of the peaks are determined on the basis of smoothened first and second derivatives, which eliminates the need for a special background subtraction. Results obtained with a computer program employing this technique are presented.

Internal conversion studies of transitions in96Mo

The internal conversion spectrum from the decay of96Tc has been investigated using a 50 cm radius double-focussing beta-ray spectrometer. Relevant features of the internal conversion spectrum from the decay of96Nb have also been reexamined in the same way. Special interest has been focussed on investigating a proposed doublet level structure at about 2.44 MeV and higher lying levels in96Mo. Internal conversion coefficients have been obtained for most transitions by combining the measured conversion electron intensities obtained in this work with recently reported gamma-ray intensities from Ge(Li) detector measurements. A level scheme has been compiled and deduced transition multipolarities have been used for a discussion of spins and parities for the levels.

Establishment of an excited state at 1.64 keV in 193Pt

Abstract A nuclear energy level of 1.64 keV in 193Pt has been established in a high-resolution study of the internal conversion spectrum in the 193Au decay. The measured half-life is 9.7 ± 0.6 ns and the de-exciting transition is most probably of M1 character.

The decay of 191Au and the level scheme of 191Pt

Abstract A total of 84 transitions in 191 Pt have been established by studying the internal conversion spectrum following the decay of 191 Au with high-resolution, magnetic, beta spectrometers. Multipolarities and mixing ratios for the strongest transitions have been deduced from K/L ratios and/or L subshell ratios. The high accuracy of the transition energy determinations together with calculated total transition intensities, established multipolarities and information from coincidence experiments enabled the construction of a consistent level scheme comprising 25 excited levels and 69 transitions. This level scheme deviates greatly from that proposed by Marklund et al. 5 ).