Picosecond transient Raman spectroscopy: The photoisomerization of trans-stilbene

We measured picosecond transient resonance Raman spectra of t-stilbene in hexane using a high repetition rate, amplified, synchronously pumped dye laser. We assign four vibrational frequencies to the olefinic moiety. Two of these frequencies, 1238 and 1565 cm−1, have broad, asymmetric bands. We attribute this band shape to a distribution of excited state molecular conformers having different single and double bond strengths.