Gamow-Teller decay of118Pd and of neighbouring even isotopes of palladium

Neutron-rich isotopes of palladium were produced via the fission of²³⁸U by 20 MeV protons. These isotopes were selected using the ion guide-fed on-line mass-separator facility IGISOL at Jyväskylä. Their decays were studied byβ-ray,γ-ray and conversion-electron spectroscopy. For¹¹⁴Pd and¹¹⁶Pd, the decay schemes established previously were confirmed; additionally multipolarities were determined for a few transitions. In the case of¹¹⁸Pd, only an approximate half-life was known from a previous radiochemical experiment. In the present study, 15 gamma transitions were observed, most of which were placed in a decay scheme. The half-life and the decay energy were found to beT _1/2=1.9±0.1 s andQ _β=4.0±0.2 MeV. The decay schemes of¹¹⁴Pd,¹¹⁶Pd and¹¹⁸Pd include — respectively — two, two and four 0⁺→1⁺ Gamow-Teller beta transitions with logft values between 4.1 and 5.1. The strength of these transitions is discussed in terms of the extreme single particle shell model with pairing and the spherical proton-neutron quasiparticle random phase approximation. The possible role of deformation is considered using a shell correction method. Predictions for the decay properties of the as yet unobserved¹²⁰Pd are given.     

Mössbauer effect study of Y(57FeMn)2

YMn₂ compound doped with⁵⁷Fe was investigated using⁵⁷Fe Mössbauer resonance in the temperature range 4.2–400 K. The magnetically split spectra were analyzed assuming two magnetically nonequivalent Fe sites with relative population dependent on iron concentration. In the transition temperature region a coexistence of the magnetic and nonmagnetic components was observed in the temperature span of about 50 K. A thermal hysteresis (of about 25 K) of the magnetic component confirms the first-order type magnetic transition. Temperature dependence of the hyperfine field of the magnetic component could be interpreted in terms of spin-fluctuation theory.     

Investigation on chemical cyclization of polyamic acid

Investigations of the chemical cyclization of polyamic acid, obtained from pyromellitic anhydride and benzidine, were performed. Using various dehydrating agents like acetyl chloride, acetic anhydride, trifluoracetic anhydride and the system acetic anhydride:pyridine (5:1), different ratios of the isoimide/imide forms were detected in the polymer by i.r. spectroscopy. A possible mechanism is suggested.