Multidimensional resonance raman spectroscopy by six-wave mixing in the deep UV Brian P. Molesky, Paul G. Giokas, Zhenkun Guo, and Andrew M. Moran Citation: The Journal of Chemical Physics 141, 114202 (2014); doi: 10.1063/1.4894846 View online: http://dx.doi.org/10.1063/1.4894846 View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/141/11?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Time-resolved broadband Raman spectroscopies: A unified six-wave-mixing representation J. Chem. Phys. 139, 124113 (2013); 10.1063/1.4821228 Tunable sideband laser from cascaded four-wave mixing in thin glass for ultra-broadband femtosecond stimulated Raman spectroscopy Appl. Phys. Lett. 103, 061110 (2013); 10.1063/1.4817915 Three wave mixing of airy beams in a quadratic nonlinear photonic crystals Appl. Phys. Lett. 97, 171102 (2010); 10.1063/1.3504247 A quantum electrodynamical treatment of second harmonic generation through phase conjugate six-wave mixing: Polarization analysis J. Chem. Phys. 109, 10580 (1998); 10.1063/1.477757 Six-wave mixing spectroscopy: Resonant coherent hyper-Raman scattering J. Chem. Phys. 108, 4013 (1998); 10.1063/1.475841
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP: 141.210.2.78 On: Mon, 24 Nov 2014 21:08:21
THE JOURNAL OF CHEMICAL PHYSICS 141, 114202 (2014)
Multidimensional resonance raman spectroscopy by six-wave mixing in the deep UV Brian P. Molesky,a) Paul G. Giokas,a) Zhenkun Guo, and Andrew M. Moranb) Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
(Received 23 February 2014; accepted 21 August 2014; published online 18 September 2014) Two-dimensional (2D) resonance Raman spectroscopies hold great potential for uncovering photoinduced relaxation processes in molecules but are not yet widely applied because of technical challenges. Here, we describe a newly developed 2D resonance Raman experiment operational at the third-harmonic of a Titanium-Sapphire laser. High-sensitivity and rapid data acquisition are achieved by combining spectral interferometry with a background-free (six-pulse) laser beam geometry. The third-harmonic laser pulses are generated in a filament produced by the fundamental and secondharmonic pulses in neon gas at pressures up to 35 atm. The capabilities of the setup are demonstrated by probing ground-state wavepacket motions in triiodide. The information provided by the experiment is explored with two different representations of the signal. In one representation, Fourier transforms are carried out with respect to the two experimentally controlled delay times to obtain a 2D Raman spectrum. Further insights are derived in a second representation by dispersing the signal pulse in a spectrometer. It is shown that, as in traditional pump-probe experiments, the six-wave mixing signal spectrum encodes the wavepacket’s position by way of the (time-evolving) emission frequency. Anharmonicity additionally induces dynamics in the vibrational resonance frequency. In all cases, the experimental signals are compared to model calculations based on a cumulant expansion approach. This study suggests that multi-dimensional resonance Raman spectroscopies conducted on systems with Franck-Condon active modes are fairly immune to many of the technical issues that challenge off-resonant 2D Raman spectroscopies (e.g., third-order cascades) and photon-echo experiments in the deep UV (e.g., coherence spikes). The development of higher-order nonlinear spectroscopies operational in the deep UV is motivated by studies of biological systems and elementary organic photochemistries. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4894846] I. INTRODUCTION
Recent experimental advances have motivated tremendous growth in the field of coherent multi-dimensional spectroscopy.1–7 The most widespread technique, twodimensional (2D) spectroscopy, employs a photon echo-like pulse sequence to overcome the tradeoff between time and frequency resolution made in traditional transient absorption experiments.8–12 The power of 2D spectroscopy has been leveraged to obtain new insights into dynamics ranging from energy transfer in photosynthesis to chemical equilibrium exchange in liquids.4, 13–22 In contrast, multi-dimensional Raman techniques are not yet widely applied because of technical challenges involved in implementation.23–25 Nonetheless, optical pump-Raman probe experiments have been used to interrogate the structural dynamics that accompany a variety of photoinduced relaxation processes (e.g., internal conversion, electron transfer). Time and frequency domain versions of Femtosecond Stimulated Raman Spectroscopy (FSRS) are capable of probing vibrational resonances in solvated chromophores throughout the entire “fingerprint” range.26–39 A second class of techniques developed by the rea) B. P. Molesky and P. G. Giokas contributed equally to this work. b) Author to whom correspondence should be addressed:
[email protected]
0021-9606/2014/141(11)/114202/25/$30.00
search groups of Scherer and Blank, referred to here as Polarizability Response Spectroscopy (PORS), is designed to detect the low-frequency (
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP: 141.210.2.78 On: Mon, 24 Nov 2014 21:08:21
THE JOURNAL OF CHEMICAL PHYSICS 141, 114202 (2014)
Multidimensional resonance raman spectroscopy by six-wave mixing in the deep UV Brian P. Molesky,a) Paul G. Giokas,a) Zhenkun Guo, and Andrew M. Moranb) Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
(Received 23 February 2014; accepted 21 August 2014; published online 18 September 2014) Two-dimensional (2D) resonance Raman spectroscopies hold great potential for uncovering photoinduced relaxation processes in molecules but are not yet widely applied because of technical challenges. Here, we describe a newly developed 2D resonance Raman experiment operational at the third-harmonic of a Titanium-Sapphire laser. High-sensitivity and rapid data acquisition are achieved by combining spectral interferometry with a background-free (six-pulse) laser beam geometry. The third-harmonic laser pulses are generated in a filament produced by the fundamental and secondharmonic pulses in neon gas at pressures up to 35 atm. The capabilities of the setup are demonstrated by probing ground-state wavepacket motions in triiodide. The information provided by the experiment is explored with two different representations of the signal. In one representation, Fourier transforms are carried out with respect to the two experimentally controlled delay times to obtain a 2D Raman spectrum. Further insights are derived in a second representation by dispersing the signal pulse in a spectrometer. It is shown that, as in traditional pump-probe experiments, the six-wave mixing signal spectrum encodes the wavepacket’s position by way of the (time-evolving) emission frequency. Anharmonicity additionally induces dynamics in the vibrational resonance frequency. In all cases, the experimental signals are compared to model calculations based on a cumulant expansion approach. This study suggests that multi-dimensional resonance Raman spectroscopies conducted on systems with Franck-Condon active modes are fairly immune to many of the technical issues that challenge off-resonant 2D Raman spectroscopies (e.g., third-order cascades) and photon-echo experiments in the deep UV (e.g., coherence spikes). The development of higher-order nonlinear spectroscopies operational in the deep UV is motivated by studies of biological systems and elementary organic photochemistries. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4894846] I. INTRODUCTION
Recent experimental advances have motivated tremendous growth in the field of coherent multi-dimensional spectroscopy.1–7 The most widespread technique, twodimensional (2D) spectroscopy, employs a photon echo-like pulse sequence to overcome the tradeoff between time and frequency resolution made in traditional transient absorption experiments.8–12 The power of 2D spectroscopy has been leveraged to obtain new insights into dynamics ranging from energy transfer in photosynthesis to chemical equilibrium exchange in liquids.4, 13–22 In contrast, multi-dimensional Raman techniques are not yet widely applied because of technical challenges involved in implementation.23–25 Nonetheless, optical pump-Raman probe experiments have been used to interrogate the structural dynamics that accompany a variety of photoinduced relaxation processes (e.g., internal conversion, electron transfer). Time and frequency domain versions of Femtosecond Stimulated Raman Spectroscopy (FSRS) are capable of probing vibrational resonances in solvated chromophores throughout the entire “fingerprint” range.26–39 A second class of techniques developed by the rea) B. P. Molesky and P. G. Giokas contributed equally to this work. b) Author to whom correspondence should be addressed:
[email protected]
0021-9606/2014/141(11)/114202/25/$30.00
search groups of Scherer and Blank, referred to here as Polarizability Response Spectroscopy (PORS), is designed to detect the low-frequency (
