Q values of the superallowed β emitters 26Alm, 42Sc, and 46V and their impact on Vud and the unitarity of the Cabibbo-Kobayashi-Maskawa matrix

The beta-decay Q(EC) values of the superallowed beta emitters Al-26(m), Sc-42, and V-46 have been measured with a Penning trap to a relative precision of better than 8x10(-9). Our result for V-46, 7052.72(31) keV, confirms a recent measurement that differed from the previously accepted reaction-based Q(EC) value. However, our results for Al-26(m) and Sc-42, 4232.83(13) keV and 6426.13(21) keV, are consistent with previous reaction-based values. By eliminating the possibility of a systematic difference between the two techniques, this result demonstrates that no significant shift in the deduced value of V-ud should be anticipated.