Knowledge Bank

We have studied the effects of a pulsed electric field on the decay dynamics of high, np $(n>30),J-1$, singlet, Rydberg levels of $H2$. We have discovered that pulsed fields of magnitudes much less than the classical value required for ionization induce a significant degree of dissociative character into levels which normally do not dissociate. This induced dissociation appears to occur during the slew of the field pulse and can be explained in terms of adiabatic passage through avoided curve crossings between the stable $J-1$ levels and the $J-0$ and 2 levels which predissociate. In addition, we have made simultaneous, high-resolution measurements of the photoionization and photodissociation spectra of molecular hydrogen in the energy region near the first ionization limit in a strong, static, external electric field. Below the classical saddle point energy, $-2|F$, electric field-induced predissociation is the dominant decay mechanism for many of the high Stark components, while above the saddle point energy the rates for field ionization and field-induced predissociation are comparable. We have also observed forced autoionization of the $|7-p\sigma ,v-1>$ level through its coupling to the structured continuum of highly excited Stark states, leading to enhanced ionization and dissociation through those Stark states which are nearly degenerate with it. These effects are explained by the unified treatment of dissociation and ionization developed by Ch. Jungen.