Deuteron-to-Proton Mass Ratio from the Cyclotron Frequency Ratio of H2+ to D+ with H2+ in a Resolved Vibrational State

We have measured cyclotron frequency ratios of H-2(+) to D+ with sufficient precision to resolve the mass increase of H-2(+) due to vibrational energy. Additional discrimination against excited vibrational levels was provided by increasing the rate of vibrational decay through Stark quenching. From our results we obtain a value for the deuteron-to-proton mass ratio, m(d)/m(p) = 1.999 007 501 274(38), which has an uncertainty three times smaller than the current CODATA value.