Valence and Rydberg states of CH sub(3)Cl: a MR-CISD study

• Published in: RSC advances Vol. 4; no. 109; pp. 64085 - 64092
• Main Authors: de Medeiros, Vanessa C, do Monte, Silmar A, Ventura, Elizete
• Format: Journal Article
• Language: English
• Published: 01.11.2014
• Subjects: Computation; Configuration interaction; Correlation; Energy use; Excitation; Mathematical analysis; Oscillator strengths; Rydberg states
• 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 similar to 9.5 eV have been calculated using highly correlated methods. The energies, spatial extent (<r super(2)>), configurations weights and oscillator strengths (f) have been computed. At the MR-CISD+Q level the excited states energies vary from similar to 7.51 to 11.98 eV. The lowest (n sigma *) excited singlet state is significantly mixed with the n3p sub(a1) and n3s Rydberg states, while the next (n3s) has a non-negligible mixture with the n sigma * state. The next three singlet states obtained result from the (n sub(Cl)) super(3)(3p sub(e)) super(1) configuration and are almost degenerate. The next (n3p sub(a1)) singlet state is significantly mixed with the n sigma * state, while the last three have sigma sub(C-Cl) arrow right Rydberg (3s or 3p) as the main configurations. According to the fvalues the most intense transition is to the 4 super(1)A sub(1) state, a sigma 3p sub(a1) Rydberg state mixed with the sigma sigma * and sigma 3s configurations. Our results indicate that the sigma sigma * configuration is responsible for the high fvalue of the gs arrow right 4 super(1)A sub(1) transition. The Rydberg-valence mixing is greatly reduced in the triplet states whose singlet counterparts have significant multiconfigurational character. The 2 super(3)A sub(1) state ( sigma sigma *) does not have its singlet counterpart, while the 4 super(1)A sub(1) state ( sigma 3p sub(a1) + sigma sigma * + sigma 3s) does not have its triplet counterpart. The obtained results are in good agreement with experimental results and with previous CASPT2 results.