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

摘要

Photo-EPR measurements carried out on Nd3+ -doped polyvinyl alcohol (PVA) ???lms 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 $|+ angle$ and $|- angle$ Zeeman components, through the decay of many excited states in the presence of magnetic ???eld or con???gurational changes around Nd3+ shifting the resonance frequency. The former appears less probable in view of the relatively slower recovery of EPR signal.