Knowledge Bank

The $B1-X$ bands of the $H2$ molecule have been studied in absorption with a 6.8 meter grazing incidence vacuum spectrograph. All the vibrational levels of the $B1$ state have been observed up to its dissociation limit. Strong heterogenous perturbation between the $B1$ and the $D1\Pi u+$ states and relatively weak homogeneous perturbation between the B and the $B1$ states have been noticed and their perturbation parameters have been determined. After deperturbation, an attempt has been made to obtain accurate rotational and vibrational constants for the $B1$ state. Since both the $Bv1$ and $\Delta G1$ curves have very peculiar shapes, which might be due to a repulsion between the B and $B1$ state at larger internuclear distances, it is difficult to represent the whole $Bv1$ and $\Delta G1$ curves by polynomial expansions. By examining the behavior of the least squares equations for the first four, five and six values of $Bv1$ and $\Delta G1$ in the region $v=0$ to $v=-1/2$, the most likely equilibrium constants for the $B1$ state are $\omega e=2039.5cm-1,\omega exe=83.41cm-1,\omega eye=3.53cm-1Be=26.349cm-1,\alpha e=1.833cm-1,\gamma e=-0.0575cm-1$ The present vibrational constants differ very much from those given by Monfils $(\omega e=2064.5cm-1,\omega exe=106.4cm-1,\omega eye=11.8cm-1)$. This is because Monfils did not carefully examine the extrapolated portion of his equation for $\Delta G1$ curve. In his case, as v tends to $-1/2$ the extrapolated portion of the curve bends upward very rapidly from the portion of the curve connecting the observed data points.