Angle-resolved photoelectron spectrometry of atomic chlorine using synchrotron radiation

Using synchrotron-radiation-based angle-resolved photoelectron spectrometry, the Cl 3s3p⁵{(}³P2,1,0ᵒ)np and 3s3p⁵{(}¹P₁ᵒ)np autoionizing Rydberg series are studied by monitoring the relative partial photoionization cross sections and asymmetry parameters of the 3p^-1 ³{P}2,1,0ᵉ$, $¹D₂ᵉ, and ¹{S}₀ᵉ$ ionic states between 21.75 and 27.75 eV. The Rydberg series converging upon the 3${s}^{{{-}}1}$ $³P₂ᵒ, ³P₁ᵒ, and ³{P}₀ᵒ$ thresholds are clearly resolved. Rydberg levels up to n=14 can be identified in the ${(}³P2,1,0ᵒ)np series, while the (¹{P}₁ᵒ$)np Rydberg series can be observed up to n=10.The relative partial cross sections are placed on an absolute scale using previous data obtained with an electron spectroscopy modulation method. The present experimental results for the Cl (³{P}2,1,0ᵒ$)np and ${(}¹P₁ᵒ)np Rydberg series are compared with those of the Ar 3s3p⁶{(}²S1/2ᵉ)np series, and with theoretical results of a nonrelativistic many-body perturbation theory calculation. The ³{P}2,1,0ᵒ$ and $¹P₁ᵒ ionization thresholds obtained from the Rydberg series agree very well with the ionization limits calculated on the basis of the Cl ii spectrum, and with the ionization energies determined from a 3s^-1 photoelectron spectrum. Autoionization phenomena due to 3s²3p⁵{→}3s²3p³nln'l' two-electron excitations are observed in the ¹{P}₁ᵒ$ resonance region.