The vibration-rotational spectrum of the hydrogen molecular ion H${\mathrm{D}}^{+}$ has been observed by means of a new ion-beam laser-resonance method employing Doppler-effect tuning and collisional detection. Six transition-frequency groups between 1642 and 1869 ${\mathrm{cm}}^{-1\mathrm{}}$, exhibiting partially resolved hyperfine structure, have been measured to ± 1 ppm. The accuracy exceeds that of present theoretical calculations of H${\mathrm{D}}^{+}$ energy levels.

• Received 13 May 1976

DOI:https://doi.org/10.1103/PhysRevLett.36.1488