Knowledge Bank

Methane's $3\nu 1+\nu 3$ vibrational overtone transition centered at 8871 {\AA} is studied with a molecular beam/Stark apparatus having 7.5 MHz doppler limited resolution. First order Stark splitting is observed for transitions between levels of E type symmetry. Because supersonic jet cooling effectively restricts population to $J\le 2$ rotational levels, we observe Stark splitting for only the $P(2),Q(2)$ and R(2) lines. From the measured splittings we estimate the magnitude of the vibrationally induced dipole moment of the $3\nu 1+\nu 3$ vibrational state.