Q value for the double-{beta} decay of {sup 136}Xe

The high-resolution, deflection-type mass spectrometer, Manitoba II, has been used to determine directly the mass difference {sup 136}Xe-{sup 136}Ba to be 2639.6 (0.6) {mu}u, giving Q{sub {beta}{beta}}=2458.7 (0.6) keV.