POWER DENSITIES FOR 2-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 transit ions for isomeric nuclei with a half-life greater than 10 min, for whi ch there is an intermediate state of known energy, spin and half-life, for which the intermediate state is connected by a known gamma-ray tr ansition to the isomeric state and to at least another intermediate st ate, and for which the relative intensities of the transitions to lowe r states are known. For the isomeric nucleus Ho-166m, 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 hav e found power densities P-2 of the order of 10(10) W cm(-2) for severa l other isomeric nuclei. [S0556-2813(98)00510-X].