Knowledge Bank

Vibration-rotation bands of diacetylene, $C4H2$, at 628, 1241, 8577, 8744, 9609, 9684, and $9717cm-1$ have been observed at high resolution and analyzed. Pressures up to 20 torr and path lengths up to 400 m were used to photograph the weaker bands. Ground state combination differences from all bands have been fitted simultaneously to give values of $B\prime \prime$ and $D\prime \prime$. Rotational constants of the excited vibrational states have also been determined; however, severe perturbations in some of the higher vibrational states preclude any simple interpretation of the effective rotational constants of these bands.""