Chlorocyclohexane Valence and Rydberg Electronic Excitations

Here we present new cross-section values of chlorocyclohexane (C₆H₁₁Cl) from vacuum ultraviolet (VUV) photoabsorption measurements in the photon energy range of 5.0-10.8 eV (115-248 nm). Theoretical calculations using time-dependent density functional theory (TD-DFT) have been performed to aid in the interpretation of the photoabsorption spectrum. The information from these calculations has allowed the assignment of the excited states in valence, mixed valence-Rydberg, and Rydberg transitions. The fine features in the photoabsorption bands have been assigned to (C-H₂)₄ symmetric stretching (and C-H stretching), <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>v</mml:mi></mml:mrow><mml:mrow><mml:mn>7</mml:mn></mml:mrow><mml:mrow><mml:mo>'</mml:mo></mml:mrow></mml:msubsup><mml:mrow><mml:mo>(</mml:mo><mml:msup><mml:mrow><mml:mi>a</mml:mi></mml:mrow><mml:mrow><mml:mo>'</mml:mo></mml:mrow></mml:msup><mml:mo>)</mml:mo></mml:mrow></mml:math>, (C-H₂)₄ wagging, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>v</mml:mi></mml:mrow><mml:mrow><mml:mn>11</mml:mn></mml:mrow><mml:mrow><mml:mo>'</mml:mo></mml:mrow></mml:msubsup><mml:mrow><mml:mo>(</mml:mo><mml:msup><mml:mrow><mml:mi>a</mml:mi></mml:mrow><mml:mrow><mml:mo>'</mml:mo></mml:mrow></mml:msup><mml:mo>)</mml:mo></mml:mrow></mml:math> and ring puckering/C-Cl stretching <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>v</mml:mi></mml:mrow><mml:mrow><mml:mn>23</mml:mn></mml:mrow><mml:mrow><mml:mo>'</mml:mo></mml:mrow></mml:msubsup><mml:mrow><mml:mo>(</mml:mo><mml:msup><mml:mrow><mml:mi>a</mml:mi></mml:mrow><mml:mrow><mml:mo>'</mml:mo></mml:mrow></mml:msup><mml:mo>)</mml:mo></mml:mrow></mml:math> modes. From the absolute cross-section values, photolysis lifetimes in the Earth's atmosphere have been estimated, showing that solar photolysis may only be considered a relevant sink at altitudes above 20 km. Additional calculations at the TD-DFT level of theory have been performed to obtain potential energy curves for the lowest-lying electronic states, highlighting the role of predissociative character.