We present three techniques for suppressing predissociation of the nitric oxide Rydberg states normally excited in pulsed-field ionization zero-kinetic-energy photoelectron spectroscopy. By applying a combination of appropriate dc and microwave fields it is possible to inhibit predissociation by resonantly mixing Stark states of adjacent principal quantum number n, with similar parabolic quantum number k. Lifetime enhancement is also obtained by using an appropriate radio-frequency field to resonantly mix Stark states of the same n. Finally, in the absence of dc fields, microwaves are used to stabilize optically excited n f Rydberg states, by inducing transitions to higher angular momentum states with longer lifetimes, specifically to the nϮ1, lу4 states.
By changing an electric field it is possible to effect the same change in configuration as by altering the time delay between two picosecond laser pulses. In particular, we demonstrate that it is possible to change excited Ba atoms from a doubly excited 5d7d state to a singly excited 6snk Rydberg state by changing an electric field by 630 V/cm.
Assignment of the first five electronic states of Ar 2 + from the rotational fine structure of pulsed-field-ionization zero-kinetic-energy photoelectron spectra
We have experimentally observed the time dependence of the population oscillation between a doubly excited state and singly excited Rydberg states subsequent to excitation by a short laser pulse. Specifically, we have examined the case in which the configuration interaction between a doubly excited state and a singly excited Rydberg series is weak. The data are quantitatively reproduced using a quantum defect theory calculation, and we contrast simple classical pictures of the population oscillation for weak and strong configuration interaction. We also observe significant, and unexpected, Raman redistribution by the final laser pulse, and we are able to demonstrate that it occurs primarily by Raman transitions via a lower state, not via the continuum.
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