Mass and QEC value of 26Si

The Q(EC) value of the superallowed beta emitter Si-26 has been measured with the JYFLTRAP Penning trap facility to be 4840.85(10) keV which is ten times more precise than any previous measurement. This leaves only the branching ratio to be improved before the Ft value of Si-26 can be used to test the conserved vector current hypothesis. As a consequence, the Al-25(p,gamma)Si-26 reaction Q-value (Q(p gamma)) was improved to be 5513.7(5) keV, limited now by the mass excess of Al-25. The new Q(p gamma) value changes the stellar production rate of Si-26 in nova ignition temperatures by about 10%.