Ultrafast Infrared Spectroscopy
Group:
Biological Physics
Contributors:
S. Erramilli,
Collaboration: Prof L. Ziegler, Chemistry; Prof Ken Rothschild, Physics; Prof M. K. Hong, Physics, Prof Feng Wang, Chemistry; Prof Richard Averitt, Physics
Graduate Students: Eric Pinnick, Logan Chieffo, Jeff Shattuck, Xihua Wang, Jason Amsden (PhD Jan 2008), Mikkel Jensen, Erica Raber
A multidisciplinary collaboration project that involves the development of an ultra fast multicolor infrared spectrometer in order to study interactions of light on fundamental biological molecules and systems.
- Single Color IR pump-probe experiments have been used to study the nature of the environment of the anesthetic gas nitrous oxide in water and model membranes. These represent the first utrafast studies on an anesthetic gas N2O, which appears to be exquisitely sensitive to the hydration state of the membrane system [with Prof Ziegler & Prof Rothschild]
- Studies on vibrational energy relaxation in water have identified a novel energy relaxation pathway, and the dynamics of the combination band [with Prof Ziegler]
- The experimental studies are combined with Molecular Dynamics simulations to identify the role of ordering of water in nanoconfined systems [with Prof Feng Wang & helpful discussions with Prof Stanley]
- Visible pump-IR probe studies are used to study photoactive proteins [Prof Rothschild] have shown that the protein backbone responds within 800 femtoseconds of photoexcitation. The studies the first time such a fast response in the protein backbone has been detected in a bacterial proteorhodosin system.
- 2-D IR femtosecond IR spectroscopy:Traditional (1D) infrared spectroscopy can, at best, obtain spectra on a nanosecond time scale, and the spectra contain ambiguously broad lineshapes, which cannot be interpreted. Utilizing multiple ultra fast pulses, varied both in time and frequency, spectra can be obtained on a timescale of several hundred femtoseconds. These multidimensional spectra provide a direct measurement of the mechanism that leads to line width broadening, as well as information on the vibrational couplings in the molecule. The data obtained can be used to determine between homogenous and inhomogeneous broadening and to monitor the structure of a molecule on a femtosecond timescale.
A spectra physics Hurricane titanium sapphire laser is used to generate 100 femtosecond pulses, which are tuned to the appropriate wavelength for experimental conditions using non-linear crystals and optical parametric amplifiers. A 64-element HgCdTe array detector is used to study the spectrum over the full bandwidth of the laser pulse.