Q Values of the Superallowed β Emitters ²⁶Al^m, ⁴²Sc, and ⁴⁶V and Their Impact on V_ud and the Unitarity of the Cabibbo-Kobayashi-Maskawa Matrix

The β-decay Q_EC values of the superallowed beta emitters ²⁶Al^m, ⁴²Sc, and ⁴⁶V have been measured with a Penning trap to a relative precision of better than 8×10^-9. Our result for ⁴⁶V, 7052.72(31) keV, confirms a recent measurement that differed from the previously accepted reaction-based Q_EC value. However, our results for ²⁶Al^m and ⁴²Sc, 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.