A generalized ADK (Ammosov–Delone–Krainov) theory for ionization of open-shell atoms is compared to ionization experiments performed on the transition metal atoms V, Ni, Pd, Ta and Nb. Our theory is found to be in good agreement for V, Ni, Pd and Ta, whereas conventional ADK theory overestimates ionization by orders of magnitude. The key to understanding the observed ionization reduction is the angular momentum barrier. Our analysis shows that the determination of the angular momentum barrier in open-shell atoms is nontrivial. The Stark shift is identified as the second dominant effect responsible for ionization suppression. Finally, these two effects cannot explain the Nb data. An analysis of the electron spins suggests that Pauli blocking might be responsible for the suppression of tunnelling in Nb.
Numerically determined ionization rates for the field ionization of atomic hydrogen in strong and short laser pulses are presented. The laser pulse intensity reaches the so-called ``barrier-suppression ionization'' regime where field ionization occurs within a few half laser cycles. Comparison of our numerical results with analytical theories frequently used shows poor agreement. An empirical formula for the ``barrier-suppression ionization'' rate is presented. This rate reproduces very well the course of the numerically determined ground-state populations for laser pulses with different length, shape, amplitude, and frequency.
Arginine kinase plays an important role in the cellular energy metabolism of invertebrates. Dimeric arginine kinase (dAK) is unique in some marine invertebrates. The effects of Zn 21 on the unfolding and aggregation of dAK from the sea cucumber Stichopus japonicus were investigated. Our results indicated that Zn 21 caused dAK inactivation accompanied by conformational unfolding, the exposure of hydrophobic surface, and aggregation. Kinetic studies showed the inactivation and unfolding of dAK followed biphasic kinetic courses. Zn 21 can affect unfolding and refolding of dAK by trapping the reversible intermediate. Our study provides important information regarding the effect of Zn 21 on