Transition Rates inCa44

The mean lives of states in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ up to an excitation energy of 3360 keV have been measured by the Doppler-shift attenuation method, using both solid and gas backings to slow the recoiling nuclei. Most of the states have lifetimes in the range of a few picoseconds, a "time region" at the limit of sensitivity of either method alone. The combination of the two methods gives accurate upper and lower limits, and a value for the mean life. The resulting experimental transition probabilities are compared to a calculation which assumes the existence of a core-excited rotational band in ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$ identical to that found to be necessary in ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$. A general agreement is obtained. A value has also been measured for the mean life of the 2750-keV 4${}_{}{}^{+}{}_{}{}^{}\mathrm{state}$ in ${}_{}{}^{42}{}_{}{}^{}\mathrm{Ca}$.