TABLE 3.

Estimated S₀ (1¹A_g^–) → S₂ (1¹B_u⁺) and S₀ (1¹A_g^–) → S₁ (2¹A_g^–) Transition Energies (in cm^–1) of Unsubstituted Linear Polyenes in Vacuum^a

polyene	S0 (11Ag–) → S2 (11Bu+) vertical transition	S0 (11Ag–) → S1 (21Ag–) vertical transition	E(11Bu+) – E(21Ag–) diff in vertical transition energies	E(11Bu+) – E(21Ag–) diff in (0–0) transition energies
octatetraene	37 110 ± 770	32 460 ± 735	4640 ± 1060	7550 ± 45
decapentaene	32 460 ± 760	27 350 ± 705	5110 ± 1040	7930 ± 165
dodecahexaene	30 210 ± 765	24 500 ± 680	5710 ± 1020	8420 ± 100
tetradecaheptaene	28 270 ± 770	22 150 ± 660	6120 ± 1040	8770 ± 150

^aThe estimated uncertainties in the S₀ (1¹Ag^–) → S₂ (1¹Bu⁺) and S₀ (1¹Ag^–) → S₁ (2¹Ag^–) vertical transition energies are half of the vibronic spacings observed in the absorption and emission spectra.