A relaxation-assisted 2D IR spectroscopy method

Department of Chemistry, Tulane University, New Orleans, LA 70118

Edited by F. Fleming Crim, University of Wisconsin, Madison, WI, and approved April 13, 2007 (received for review January 22, 2007)

Abstract

A method of two-dimensional infrared (2D IR) spectroscopy called relaxation-assisted 2D IR (RA 2DIR) is proposed that utilizes vibrational energy relaxation transport in molecules to enhance cross-peak amplitudes. This method substantially increases the range of distances accessible by 2D IR and is capable of identifying long-range connectivity patterns in molecules. RA 2DIR is illustrated in interactions among CN and CO modes in 3-cyanocoumarin and 4-acetylbenzonitrile, where the distances between the CN and CO groups are ≈3.1 and ≈6.5 Å, respectively. A 6-fold increase in cross-peak amplitude was observed in 4-acetylbenzonitrile when the dual-frequency RA 2DIR method was used.

Footnotes

^†To whom correspondence should be addressed. E-mail: irubtsov{at}tulane.edu
Author contributions: I.V.R. designed research; D.V.K. and S.R.G.N. performed research; D.V.K. and I.V.R. analyzed data; and I.V.R. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0700560104/DC1.
↵ ‡ Ding, F., Fulmer, E. C., Zanni, M. T., 15th International Conference on Ultrafast Phenomena, Optical Society of America, July 31–Aug. 4, 2006, Pacific Grove, CA.
↵ § Kurochkin, D. V., Naraharisetty, S. G., Rubtsov, I. V., 15th International Conference on Ultrafast Phenomena, Optical Society of America, July 31–Aug. 4, 2006, Pacific Grove, CA.
↵ ¶ Kim, Y. S., Hochstrasser, R. M., 15th International Conference on Ultrafast Phenomena, Optical Society of America, July 31–Aug. 4, 2006, Pacific Grove, CA.
Abbreviations:

AcPhCN,

4-acetylbenzonitrile;

IVR,

intramolecular vibrational energy redistribution;

LO,

local oscillator;

RA 2DIR,

relaxation-assisted 2D IR;

T-delay,

time delay T.