Photoabsorption cross sections of CH4, CF4, CF3Cl, SF6, and C2F6 from 175 to 770 Å

Abstract

Using synchrotron radiation as a continuum background, the photoabsorption cross sections of CH₄, CF₄, CF₃Cl, SF₆, and C₂F₆ were measured photoelectrically in the 175–770 Å region. Discrete structure was observed and attributed to the Rydberg states converging to the known states of the ions: In CH₄, Rydberg states converging to the (2a₁)⁻¹ ion state with vibrational frequencies varying from 1800 to 2200 cm⁻¹ were observed in the 563–627 Å region. In CF₄, Rydberg states converging to the (4a₁)⁻¹ and (3t₂)⁻¹ ion states with vibrational frequencies varying from 550 to 730 cm⁻¹ were observed in the 559–611 Å region. ’’Window’’ type Rydberg states converging to the (4a₁)⁻¹ ion states were also observed. In CF₃Cl, discrete structure with energy spacings varying from 540 to 700 cm⁻¹ was observed in the 614–666 Å region. The assignment of this structure to Rydberg states was not attempted because the vibrational structure of the CF₃Cl ion states is not known. In SF₆, structure was observed in the 630–676 Å region and was attributed to the Rydberg states converging to the (1t_2g)⁻¹ ion state.