Metastable state decay

NIS measurements (at 77 K) were also performed on a GNP single crystal (c-cut) (a) after the sample was illuminated with blue light (450 nm) at 50 K to populate metastable molecular states and (b) after warming up the illuminated crystal to 250 K at which the metastable states decay to the groundstate [94]. Comparison of measured and simulated (DFT) NIS spectra provided evidence for the isonitrosyl structure of the metastable state MSi [95] which was proposed earlier by Carducci et al. in their pioneering X-ray study [96]. 

In many cases of physical interest (e.g., a decay, photoionization, or predissociation) the dynamic and the dissipative subsystems correspond to degenerate (or quasidegenerate) states of the same zero-order Hamiltonian. For future purposes, it will be useful to establish the way in which a metastable state decays in this case. Let the total Hamiltonian for the system be given by... 

By direct substitution in eq. (2-44) we then see that the metastable state decays exponentially with the mean lifetime P1. 

Formula (3.53) demonstrates that the decay rate for a metastable state is equal to the inverse period of classical vibrations in the well (attempt frequency) times the barrier transparency. The more traditional treatment of metastable-state decay using the one-dimensional WKB approximation is given in Appendix A. 

The Cs/ Ba decay scheme in Fig. 9.5 shows two beta-particle groups emitted by Cs. The 1176-keV maximum-energy beta-particle group decays to the ground state in 5.6% of the decays and the 514-keV maximum-energy beta-particle group decays in 94.4% of the decays to an excited state in The Ba is in secular equilibrium with Cs. This metastable state decays with a 2.55-min half-life. The decay of Ba is 85.1% by 661-keV gamma rays and 9.4% by conversion electrons. 

Zampedri et al. have shown that, in (100 — x)Si02-(x)Ti02-lEr03/2 planar waveguides prepared by sol-gel route, for x < 12, about 65% of the Er + ions in the Ii3/2 metastable state decay exponentially with a lifetime of about 8 ms (Zampedri, 2003). 

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