All-valence-electron CI treatment of the electronic spectrum of trans-butadiene

✍ Scribed by Robert J. Buenker; S. Shih; S.D. Peyerimhoff

• Publisher: Elsevier Science
• Year: 1976
• Tongue: English
• Weight: 941 KB
• Volume: 44
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(76)80536-2

✦ Synopsis

An all-valenceclectron

CI treatment is reported for the low-lying valence and Rydberg states of butadicne. AII singIyand doubly-excited configurations rclativc to a series of the leading terms in a given CI expansion are taken into account, with resulting secular equation orders of as high as 150 000. The agreement between calculated and experimental transition energies IS invariably better than 0.2 eV where comparison is possible, with alI low-lying valence triplet and Rydbey singlet excited states being unambiguously assigned. .The valence-shell excitation to the 2 'Ag species is concIuded to correspond to the 7.06 CV band system, while the forbidd$n singlet--singlet transition rcportcd by hfcDiarmid is assigned as x2 + 3s. The possibility of an avoided crossing between Rydbeg valence '9, excited states having d determining infhxcnce on the appearance of the broad intense V, -N absorption system is also discussed.