Alpha particle energies were redetermined to an accuracy of 2 to 5 keV for a group of 40 neutron-deficient nuclides with atomic numbers ranging from 65 to 88. Improved half-life values were measured for 10 of these nuclides. Weightless samples containing mixtures of these activities were prepared by use of the helium jet transport technique to remove spallation and fragmentation products recoiling from targets of U, Th, Au, and Ta bombarded with 5 GeV protons. Experimental and calibration techniques are discussed in detail. Implications of the results for the mechanism of reaction of 5 GeV protons with complex targets are briefly discussed.

RADIOACTIVITY 5 GeV $p$ + U, Th, Au, Ta; separated recoil products by helium jet; measured $E\alpha$, $t_{\frac{1}{2}}$ ${}_{}{}^{151}{}_{}{}^{}\mathrm{Dy}$, ${}_{}{}^{154}{}_{}{}^{}\mathrm{Er}$, ${}_{}{}^{150}{}_{}{}^{}\mathrm{Dy}$, ${}_{}{}^{152}{}_{}{}^{}\mathrm{Ho}$, ${}_{}{}^{152}{}_{}{}^{}\mathrm{Ho}_{}^m{}_{}{}^{}$, ${}_{}{}^{151}{}_{}{}^{}\mathrm{Ho}$, ${}_{}{}^{151}{}_{}{}^{}\mathrm{Ho}_{}^m{}_{}{}^{}$, ${}_{}{}^{153}{}_{}{}^{}\mathrm{Er}$, ${}_{}{}^{152}{}_{}{}^{}\mathrm{Er}$, ${}_{}{}^{154}{}_{}{}^{}\mathrm{Tm}$, ${}_{}{}^{154}{}_{}{}^{}\mathrm{Tm}_{}^m{}_{}{}^{}$, ${}_{}{}^{153}{}_{}{}^{}\mathrm{Tm}$, ${}_{}{}^{179}{}_{}{}^{}\mathrm{Pt}$, ${}_{}{}^{155}{}_{}{}^{}\mathrm{Yb}$, ${}_{}{}^{178}{}_{}{}^{}\mathrm{Pt}$, ${}_{}{}^{177}{}_{}{}^{}\mathrm{Pt}$, ${}_{}{}^{176}{}_{}{}^{}\mathrm{Pt}$, ${}_{}{}^{199}{}_{}{}^{}\mathrm{Po}_{}^m{}_{}{}^{}$, ${}_{}{}^{198}{}_{}{}^{}\mathrm{Po}$, ${}_{}{}^{212}{}_{}{}^{}\mathrm{Fr}$, ${}_{}{}^{197}{}_{}{}^{}\mathrm{Po}_{}^m{}_{}{}^{}$, ${}_{}{}^{213}{}_{}{}^{}\mathrm{Fr}$, ${}_{}{}^{212}{}_{}{}^{}\mathrm{Ra}$; measured $E\alpha$ ${}_{}{}^{149}{}_{}{}^{}\mathrm{Tb}$, ${}_{}{}^{211}{}_{}{}^{}\mathrm{At}$, ${}_{}{}^{204}{}_{}{}^{}\mathrm{Fr}$, ${}_{}{}^{222}{}_{}{}^{}\mathrm{Ac}$, ${}_{}{}^{217}{}_{}{}^{}\mathrm{At}$, ${}_{}{}^{218}{}_{}{}^{}\mathrm{Rn}$, ${}_{}{}^{219}{}_{}{}^{}\mathrm{Fr}$, ${}_{}{}^{211}{}_{}{}^{}\mathrm{Po}$, ${}_{}{}^{214}{}_{}{}^{}\mathrm{Po}$, ${}_{}{}^{217}{}_{}{}^{}\mathrm{Rn}$, ${}_{}{}^{216}{}_{}{}^{}\mathrm{At}$, ${}_{}{}^{218}{}_{}{}^{}\mathrm{Fr}$, ${}_{}{}^{215}{}_{}{}^{}\mathrm{At}$, ${}_{}{}^{213}{}_{}{}^{}\mathrm{Po}$, ${}_{}{}^{212}{}_{}{}^{}\mathrm{Po}$, ${}_{}{}^{214}{}_{}{}^{}\mathrm{At}$, ${}_{}{}^{211}{}_{}{}^{}\mathrm{Po}_{}^m{}_{}{}^{}$; reaction mechanisms discussed.

• Received 21 September 1981

DOI:https://doi.org/10.1103/PhysRevC.25.941