The recurrence spectroscopy of atomic argon and the classical nature of quantum spectra

This work populates the J=2 metastable state of atomic argon in a fast beam via near-resonant charge-transfer with potassium vapor and uses a frequency-doubled pulsed-dye-laser to perform UV classically-scaled Stark-spectroscopy of bound Rydberg-states converging to the j=3/2 ionization limit and, by incorporating a novel detector system, autoionizing Rydberg-states converging to the j=1/2 ionization limit.;Stark spectroscopy below the j=3/2 ionization limit produced data over a wide range of effective principal quantum number around n=20 and scaled energies of |epsilon| = infinity to 1.7. The analysis employed Fourier and wavelet transforms of the absorption spectra with respect to n to obtain recurrence spectra. The Fourier-transform shows recurrences associated with inelastic collisions between the Rydberg electron and the excited ion-core. The wavelet transform shows diffusion of recurrence probability into broad peaks and n-dependent regions of enhancement and suppression of hydrogenic Stark-orbits. The wavelet transform also shows the capability to extract orbital periods in the time domain by transforming with respect to the energy.;Above the j=3/2 ionization limit, inelastic scattering with the excited ion-core destabilizes the classical orbit of the Rydberg electron producing autoionization, and an Ericson regime in the Stark spectrum is suggested. The data shows an exponential decay in the recurrence probability as a function of the number of core returns. Extracting a decay rate shows that the Rydberg electron makes an average of ten core passes before ionization. This observation supports the Gutzwiller conjecture that the stability of unstable periodic orbits is described by an exponential decay that depends on the Lyapunov exponent. The absorption spectrum of autoionizing argon shows peaks that are near Lorentzian, consistent with the Gutzwiller conjecture, but more accurately described as Fano profiles. Several absorption peaks have been fit to extract the Fano parameters.