Emission of Gamma Rays by X-ray Electron-Nuclear Double Transitions

This is a paper about induced gamma emission. The X-ray electron-nuclear double transitions (XENDT) are processes in which a transition effected by an inner atomic electron takes place simultaneously with a nuclear electromagnetic transition. We give expressions for the cross sections of electric and magnetic XENDTs of various multipole orders. We calculate the rate of deexcitation of isomeric nuclei induced by XENDTs for the case when the holes in the atomic shells are produced by incident ionizing electrons and find that the induced nuclear deexcitation rate becomes comparable to the natural decay rate for ionizing fluxes of the order of $10^{14}$ W cm$^{-2}$. We show that for E1 and M1 nuclear processes for which there is a matching between the electron and the nuclear transition energies, the XENDTs can be used to produce pulses of M\"{o}ssbauer radiation, with yields of the order of $10^4$ Bq mA$^{-1}$.Comment: 16 pages, 2 Postscript figures; please print Tables I, II and III with the latex option: tr1 , which produces a 90-degree rotation of the pag

Power densities for two-step gamma-ray transitions from isomeric states

We have calculated the incident photon power density P_2 for which the two-step induced emission rate from an isomeric nucleus becomes equal to the natural isomeric decay rate. We have analyzed two-step transitions for isomeric nuclei with a half-life greater than 10 min, for which there is an intermediate state of known energy, spin and half-life, for which the intermediate state is connected by a known gamma-ray transition to the isomeric state and to at least another intermediate state, and for which the relative intensities of the transitions to lower states are known. For the isomeric nucleus 166m-Ho, which has a 1200 y isomeric state at 5.98 keV, we have found a value of P_2=6.3 x 10^7 W cm^{-2}, the intermediate state being the 263.8 keV level. We have found power densities P_2 of the order of 10^{10} W cm^{-2} for several other isomeric nuclei.Comment: 9 pages, 1 eps figure, 1 tabl