DENSITY EFFECT ON NEWLY IDENTIFIED HIGH-N RYDBERG SERIES OF KRYPTON BY A RESONANTLY ENHANCED MULTIPHOTON IONIZATION METHOD

Four even-parity atomic series corresponding to transitions from the 5s[1/2]10 level to the (2P3/20)np,nf levels of krypton have been observed, using a resonant multistep two-color photoionization method. The energies of 7p[3/2]1, 7p[1/2]1, 7p[3/2]2, 7p[1/2]0, np[1/2]1, np[3/2]2, np[1/2]0, and nf[3/2]1,2 levels are determined and the principal quantum numbers are calculated for n up to 45, 32, 49, and 44, respectively. Strong spectral irregularities in intensity and position are analyzed with the help of Lu-Fano diagrams and multichannel quantum defect theory in the case of the most intense 5s[1/2]10np[1/2]0 series. Density shift rates have the constant value of -7.4(2)×10-19 cm-1/cm-3 for the sp high-n series members, outside regions where irregularities are observed, in agreement with existing doped krypton data. A close agreement with the Fermi model is obtained for these high-n members of regular series. Departure from this agreement is found for members whose excited levels are mixed with 7p states. A clear relationship between the pp admixture and shift rate decrease, in regions of irregularities, is demonstrated. © 1990 The American Physical Society.