Fluorescence from the S1(2 1Ag) state of all-trans-β-carotene

Nonlinear optical and electroabsorption spectra of polydiacetylene crystals and films

“…Maximum overlap is seen from ͑1͒ to occur at E 2A ϭ2E 1B /3, which is almost the ␤-carotene case, 44 and leads to five-fold enhancement. 9 The need for additional A states was recognized in phenomenological THG fits 45 of ␤-carotene, consistent with ͑23͒.…”

β‐Carotene Revisited by Transient Absorption and Stimulated Raman Spectroscopy

“…[44].The spectrum is dominated by two lines, at 1155 and 1520 cm .Al ine at 1448 cm À1 represents asymmetric methyl deformations. A weak shoulder at 1192 cm À1 is attributed to aC ÀCs tretching mode located at C 8 andC 9 .T he weak Ramanl ine at 1600 cm À1 is caused by C=Cs tretching between C 7 and C 8 .T he assignment of the weak band at 874 cm À1 is uncertain butm ay originate from CÀCs tretching modes of the b-rings.R amana ctivity in the low-frequency region is very small;f rom critical analysis we conclude weak lines at 234, 299, 429, 519 and 600 cm À1 . Observed andc alculated S 0 Ramanl ines are listed in Ta ble S1.…”

“…[4] The energy of S 1 was estimatedat n 1 % 14 000 cm À1 above S 0 (1A g À ) [5,6] and confirmed experimentally, when the S 2 -S 1 transition energy (n 2 -n 1 )w as subtracted from n 2 . [7] While the lifetime of S 1 does not depend on the environment, [8,9] , the S 2 (1B u + )s tate is highly polarizable and thus, influencedb y the solvent. [9,10] Ab road excited-statea bsorption band S x !…”

“…[7] While the lifetime of S 1 does not depend on the environment, [8,9] , the S 2 (1B u + )s tate is highly polarizable and thus, influencedb y the solvent. [9,10] Ab road excited-statea bsorption band S x ! S 2 was recorded in the near-infrared (NIR) which decaysw ith % 200 fs.…”

“…Overlaido nt he decay of S 1 excited-state absorption, ap icosecond process is found that is absent when the C 9 -methyl group is replaced by ethyl or isopropyl. It is attributed to reorganization on the S 1 potential energy surface, involving dihedral angles between C 6 and C 9 .InR aman studies, electronic states S 2 or S 1 weres elected through resonance conditions. We observe ab road vibrational band at 1770 cm À1 in S 2 already.W ith 200 fs it decays and transforms into the wellknownS 1 Ramanl ine for an asymmetric C=Cs tretching mode.…”