Valence and Rydberg states of CH3Cl: a MR-CISD study

• Main Authors: de Medeiros, Vanessa C, do Monte, Silmar A, Ventura, Elizete
• Format: Journal Article
• Language: English
• Published: 01.01.2014
• ISSN: 2046-2069
• DOI: 10.1039/c4ra10567b

In this work ten singlet and nine triplet states are studied through multi-reference configuration interactions with singles and doubles (MR-CISD), including Davidson extensivity correction (MR-CISD+Q). For the first time the excited states whose energies are larger than ∼9.5 eV have been calculated using highly correlated methods. The energies, spatial extent (〈 r 2 〉), configurations weights and oscillator strengths ( f ) have been computed. At the MR-CISD+Q level the excited states energies vary from ∼7.51 to 11.98 eV. The lowest (nσ*) excited singlet state is significantly mixed with the n3p a1 and n3s Rydberg states, while the next (n3s) has a non-negligible mixture with the nσ* state. The next three singlet states obtained result from the (n Cl ) 3 (3p e ) 1 configuration and are almost degenerate. The next (n3p a1 ) singlet state is significantly mixed with the nσ* state, while the last three have σ C-Cl → Rydberg (3s or 3p) as the main configurations. According to the f values the most intense transition is to the 4 1 A 1 state, a σ3p a1 Rydberg state mixed with the σσ* and σ3s configurations. Our results indicate that the σσ* configuration is responsible for the high f value of the gs → 4 1 A 1 transition. The Rydberg-valence mixing is greatly reduced in the triplet states whose singlet counterparts have significant multiconfigurational character. The 2 3 A 1 state (σσ*) does not have its singlet counterpart, while the 4 1 A 1 state (σ3p a1 + σσ* + σ3s) does not have its triplet counterpart. The obtained results are in good agreement with experimental results and with previous CASPT2 results. In this work ten singlet and nine triplet states are studied through multi-reference configuration interactions with singles and doubles (MR-CISD), including Davidson extensivity correction (MR-CISD+Q).