Character and spectra of triplet states in short polyenes Original Research Article

Multi-configuration quadratic response calculations with complete account of the spin—orbit coupling operator are performed to study the singlet—triplet absorption and emission spectra of the short polyenes; ethene, trans-1,3-butadiene and trans-1,3,5-hexatriene molecules. The emission spectra are calculated from geometry optimized triplet states. The missing phosphorescence in these compounds are explained as a combination of small oscillator strengths and vibrational quenching.