A K Ganguly
Articles written in Pramana – Journal of Physics
Volume 11 Issue 5 November 1978 pp 591-594 Nuclear and Particle Physics
According to Order-Disorder Model (ODM), in the early stages of fission, the charges in a fissioning nucleus gets polarised into two impending parts along with corresponding most stable neutrons which are calculated from the minimum in isobaric mass parabola. This polarisation into two most stable configuration leaves a small number of neutrons as balance neutrons i.e.
Volume 13 Issue 5 November 1979 pp 495-512 Nuclear And Particle Physics
The order-disorder model has been used to explain asymmetry of mass and charge division and related phenomena in fission. According to this model the fission process involves two steps consisting of charge polarisation into two ‘impending fragment clusters’ with beta stable neutron numbers and subsequent distribution of the balance neutrons between the two. Mode of elemental division of the fissioning nuclei is attributed to the charge polarisation in the first step. Theory of reaction rate has been applied to the system.
The frequency term is obtained by applying the conditional stochastic process under charge polarisation constraint and the energy-dependent term is given by the condition of minimum in free energy of the system. Using this, the relative probability of polarisation into given charge pair is arrived at.
The model uses stable neutron numbers for the charges as the only input. No explicit assumption or quantification on the preference of formation of shell closure species in fission is necessary. The statistics developed on the principle of equal
Volume 14 Issue 2 February 1980 pp 165-173 Solid State Physics
A new peak at about 650°C has been observed in the thermoluminescence emission of gamma irradiated natural fluorites containing significant quantities of lanthanide rare-earth (RE) elements as impurities. Thermal activation energy of the corresponding trap has been evaluated to be 2·99 eV with a frequency factor of 1016 sec−1. The optical activation energy, as deduced from photo-transfer-induced-TL from this trap, is 5·36 eV. Many types of natural fluorites as well as synthetically grown CaF2 crystals doped with single and pairs of rare earth elements have been studied and the results indicate that the high temperature peak is associated with Sm impurity coexisting with Y, La or Ce in CaF2. There are indications that this newly observed TL peak can be gainfully employed in ultraviolet dosimetry and geological dating of fluorite deposits.
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