• A R Dhobale

      Articles written in Pramana – Journal of Physics

    • Internal irradiation effects in239Pu doped K2Ca2(SO4)3): EPR, TSL and PAS investigations

      T K Seshagiri V Natarajan A R Dhobale M D Sastry

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      The electron/hole trapped centres created during internal irradiation in239Pu doped K2Ca2(SO4)3 were investigated using electron paramagnetic resonance (EPR), thermally stimulated luminescence (TSL) and photoacoustic spectroscopic studies (PAS). These techniques were used to identify the defects and characterize the thermally induced relaxation processes. TSL studies of self (α)/γ-irradiated239Pu doped K2Ca2(SO4)3 revealed two glow peaks around 400 and 433K. Plutonium introduced as Pu4+ was partly reduced to Pu3+ due to self irradiation. This was ascertained from PAS studies. EPR studies carried out on these samples showed the formation of radical ions SO4, SO3, O3, etc. The thermal destruction of SO4 ion was found to be associated with the prominent glow peak around 433K. Pu3+ was found to act as luminescent centre for the observed TSL glow. The trap depth for the glow peak at 433K has been determined from TSL and EPR data.

    • Non-equilibrium effects in copper vapor laser pumped Nd3+ doped PVA film: Photo-electon paramagnetic resonance and photoacoustic spectral investigations

      Mithlesh Kumar Y Babu A R Dhobale R M Kadam M D Sastry

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      Photo-EPR measurements carried out on Nd3+ -doped polyvinyl alcohol (PVA) films have shown that nearly 100% reduction occurs in the intensity of EPR of Nd3+ under in situ copper vapor laser (CVL) illumination (510.5 nm and 578.2 nm). The kinetics of decay and recovery were investigated. Photoacoustic (PA) spectra, observed under CVL pump condition had shown that the CVL induced changes were not due to photoinduced valence change, and that the CVL pumping creates highly favorable conditions for non-equilibrium population distribution in the excited electronic states. The complete disappearance of EPR under CVL pumping is attributed either to the possible equalization of population of |+〈 and |−〈 Zeeman components, through the decay of many excited states in the presence of magnetic field or configurational changes around Nd3+ shifting the resonance frequency. The former appears less probable in view of the relatively slower recovery of EPR signal.

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