K-SHELL FLUORESCENCE YIELDS OF MEDIUM AND HEAVY-ELEMENTS USING A SIMPLE METHOD

K-shell fluorescence yields, omega(K), of medium and heavy elements in the atomic number range 62 less than or equal to Z less than or equal to 83 at incident photon energies of 123.6 and 320 keV were measured by adopting the simple method proposed earlier, using an NaI(Tl) detec tor coupled to an active filter amplifier and a 1K multi-channel analy ser. The intensities were measured by placing the source and the targe t right on the face of the detector and by employing very weak radioac tive sources (Co-57 and Cr-51) Of the order of 10(4) Bq. Measured valu es were compared with the recent standard fitted values of Hubbell et al., and were found to be in close agreement. The omega(K) values of b ismuth, gold, tungsten, gadolinium and samarium were measured for the first time. (C) 1998 John Wiley & Sons, Ltd.