15min:

TH. A. PAUL, J. LIU AND F. MERKT, Laboratorium für Physikalische Chemie, ETH-Zürich, 8093 Zürich, Switzerland.

Using a Fourier-transform-limited, tunable vacuum-ultraviolet laser system with a 50MHz bandwidth\footnoteTh. A. Paul and F. Merkt, J. Phys. B: At. Mol. Opt. Phys. , \underline\textbf38, 4145 (2005) in conjunction with an ultra-high-vacuum spectrometer, observation of the autoionizing Rydberg series up to principal quantum number n 300 by photoionization spectroscopy allowed the determination of the ²P_1/2 ionization threshold for ^AKr (with A = 80, 82, 83, 84, 86), as well as measurement of the relative isotope shifts. The average ²P_1/2 ionization energy, weighted by natural abundances, amounts to (118284.7269 \pm(0.011) _stat \pm(0.027) _abs) cm^-1. For ⁸³Kr, an accurate determination of the hyperfine ionization thresholds with F⁺\!=\!4 and F⁺\!=\!5 was made and the magnetic dipole hyperfine coupling constant A_1/2 of the ²P_1/2 spin-orbit excited state of Kr⁺ was found to be -0.0385(5) cm^-1. The presence of a nonzero nuclear spin (I=9/2) in ⁸³Kr profoundly alters the appearance of the photoionization spectrum. Hyperfine-induced J mixing and stroboscopic resonances lead to characteristic spectral patterns that could be fully explained by multichannel quantum defect theory using the method previously developed to analyze similar patterns observed in the spectrum of autoionizing Rydberg states of Xe.\footnoteH. J. Wörner, M. Grütter, E. Vliegen and F. Merkt, Phys. Rev. A , \underline\textbf71, 052504 (2005)