Abstract
Synchrotron radiation is used to excite Ar to the intermediate states 3 p 12 5 (3 d′ [32]1, 5 d′ [3 2]1, 5 s′ [1 2]1, 7 s′ [1 2]1) and 3 p 3 2 5 (6d [1 2]1, 6d [3 2]1, 8s [3 2]1), then excited by lasers to the autoionizing Rydberg series 3 p 1 2 5 n p′ ([1 2]0,1, [3 2]1,2) and n f′ [5 2]2. For the intermediate states of 5 s′, 7 s′, and 8s, the n p′ ([1 2]0 and [3 2]2) series are observed with high intensity but not the n p′ ([1 2]1 and [3 2]1) series when the polarization vectors of two light beams are in parallel; but when they are in orthogonal, the n p′ [1 2]0 series disappears, the n p′ [3 2]2 intensity remains, and the n p′ ([1 2]1 and [3 2]1) series show up strongly. The intensity distribution of the n p′ series strongly depends on the intermediate state. The spectra of the n p′ series are assigned according to their intensity variation with the polarization vectors. The quantum defects determined for the series n p′ [1 2]0 (n=11-57), n p′ [3 2]2 (n=11-65), n p′ [3 2]1 (n=11-31), and n f′ [5 2]2 (n=9-74) are 1.611±0.011, 1.683±0.013, 1.688±0.010, and 0.016±0.005, respectively. Our values are in excellent agreement with theoretical prediction. The spectral line shapes of autoionizing Rydberg states are analyzed with a Beutler-Fano profile. Reduced autoionization linewidths for the n p′ [1 2]0 (n=11-16) series vary in the range 2549-4145 cm-1, and the n f′ [5 2]2 (n=9-11) series in 186-247 cm-1 in reasonable agreement with theoretical prediction. © 2008 The American Physical Society.