Femtosecond characterization of vibrational optical activity of chiral molecules

Hanju Rhee, Young Gun June, Jang Soo Lee, Kyung Koo Lee, Jeong Hyon Ha, Zee Hwan Kim, Seung Joon Jeon, Minhaeng Cho

Research output: Contribution to journalArticlepeer-review

154 Citations (Scopus)


Optical activity is the result of chiral molecules interacting differently with left versus right circularly polarized light. Because of this intrinsic link to molecular structure, the determination of optical activity through circular dichroism (CD) spectroscopy has long served as a routine method for obtaining structural information about chemical and biological systems in condensed phases. A recent development is time-resolved CD spectroscopy, which can in principle map the structural changes associated with biomolecular function and thus lead to mechanistic insights into fundamental biological processes. But implementing time-resolved CD measurements is experimentally challenging because CD is a notoriously weak effect (a factor of 10 -4-10-6 smaller than absorption). In fact, this problem has so far prevented time-resolved vibrational CD experiments. Here we show that vibrational CD spectroscopy with femtosecond time resolution can be realized when using heterodyned spectral interferometry to detect the phase and amplitude of the infrared optical activity free-induction-decay field in time (much like in a pulsed NMR experiment). We show that we can detect extremely weak signals in the presence of large achiral background contributions, by simultaneously measuring with a femtosecond laser pulse the vibrational CD and optical rotatory dispersion spectra of dissolved chiral limonene molecules. We have so far only targeted molecules in equilibrium, but it would be straightforward to extend the method for the observation of ultrafast structural changes such as those occurring during protein folding or asymmetric chemical reactions. That is, we should now be in a position to produce 'molecular motion pictures' of fundamental molecular processes from a chiral perspective.

Original languageEnglish
Pages (from-to)310-313
Number of pages4
Issue number7236
Publication statusPublished - 2009 Mar 19

ASJC Scopus subject areas

  • General


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