Deuteron-to-Proton Mass Ratio from the Cyclotron Frequency Ratio of H_{2}^{+} to D^{+} with H_{2}^{+} 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.