Publications

Simulations of the Two-Dimensional Electronic Spectroscopy of the Photosystem II Reaction Center

Fri, 21 Dec 2012 17:00:57 -0500

Kristin L. M. Lewis, Franklin D. Fuller, Jeffrey A. Myers, Charles F. Yocum, Shaul Mukamel, Darius Abramavicius, and Jennifer P. Ogilvie, Journal of Physical Chemistry A, ASAP article.

We report simulations of the two-dimensional electronic spectroscopy of the Qy band of the D1-D2-Cyt b559 photosystem II reaction center at 77 K. We base the simulations on an existing Hamiltonian that was derived by simultaneous fitting to a wide range of linear spectroscopic measurements and described within modified Redfield theory. The model obtains reasonable agreement with most aspects of the two-dimensional spectra, including the overall peak shapes and excited state absorption features. It does not reproduce the rapid equilibration from high energy to low energy excitonic states evident by a strong cross-peak below the diagonal. We explore modifications to the model to incorporate new structural data and improve agreement with the two-dimensional spectra. We find that strengthening the system−bath coupling and lowering the degree of disorder significantly improves agreement with the cross-peak feature, while lessening agreement with the relative diagonal/antidiagonal width of the 2D spectra. We conclude that two- dimensional electronic spectroscopy provides a sensitive test of excitonic models of the photosystem II reaction center and discuss avenues for further refinement of such models.

Probing Photosynthetic Energy and Charge Transfer with Two-Dimensional Electronic Spectroscopy

Tue, 7 Feb 2012 21:38:59 -0500

Kristin L. M. Lewis and Jennifer P. Ogilvie

Two-dimensional electronic spectroscopy (2DES) has emerged as a powerful method for elucidating the structure−function relationship in photosynthetic systems. In this Perspective, we discuss features of two-dimensional spectroscopy that make it highly suited to address questions about the underlying electronic structure that guides energy- and charge- transfer processes in light-harvesting materials. We briefly describe a pulse-shaping-based implementation of two-dimensional spectroscopy that is making the method widely accessible to problems spanning frequency regimes from the ultraviolet to the mid-infrared. We illustrate the utility of 2DES in the context of our recent studies of the primary energy-transfer and charge separation events in the photosystem II reaction center, discussing remaining challenges and speculating about exciting future directions for the field of multidimensional spectroscopy.

Multiplex Raman induced Kerr effect microscopy

Wed, 4 Jan 2012 08:18:00 -0500

Brandon R. Bachler, Martin E. Fermann, and Jennifer P. Ogilvie, Optics Express, Vol. 20, Issue 2, pp. 835-844 (2012).

We report spectrally-resolved chemical imaging based on Raman induced Kerr effect spectroscopy (RIKES). When used with circularly-polarized pump excitation, multiplex RIKES offers the potential for spectrally-resolved imaging free of the nonresonant background that plagues coherent anti-Stokes Raman scattering. RIKES does however have a highly sample-dependent birefringent background that limits its sensitivity and can introduce spectral distortions. We demonstrate that in low birefringence samples multiplex RIKES microscopy offers an enhanced signal-to-noise ratio compared to multiplex stimulated Raman scattering (SRS) when implemented in a high polarization-purity, low frequency chopping scheme.

Toward broadband two-dimensional electronic spectroscopy: correction of chirp from a continuum probe

Sat, 12 Mar 2011 14:59:04 -0500

Patrick A. Tekavec, Kristin L. M. Lewis, Franklin D. Fuller, Jeffrey A. Myers and Jennifer P. Ogilvie, in press, Journal of Special Topics in Quantum Electronics.

Recent implementations of two-dimensional spectroscopy in the pump-probe geometry using a pulse-shaper demonstrate the ease with which frequency-resolved pump-probe experiments can be readily adapted to two-dimensional methods. Many frequency-resolved pump-probe experiments employ continuum probes to observe a broad range of electronic transitions. These continuum probes are often chirped, leading to distortions that can be post-corrected by characterizing the chirp and appropriately adjusting the observed wavelength-dependent pump-probe time delay. We present an analogous chirp-correction scheme for two-dimensional spectroscopy, facilitating the use of continuum probing to expand the frequency information available in two-dimensional spectroscopy experiments. We demonstrate the method through experiments and simulations of a laser dye in solution.

Two dimensional electronic spectroscopy of the D1-D2-cytb559 photosystem II reaction center complex

Sat, 28 Aug 2010 21:56:34 -0400

Jeffrey A. Myers, Kristin L. M. Lewis, Franklin D. Fuller, Patrick F. Tekavec, Charles F. Yocum and Jennifer P. Ogilvie, Journal of Physical Chemistry Letters, 1 (19), 2774–2780

We present two-dimensional electronic spectra of isolated D1-D2-cyt-b559 reaction centers (PSII RC) at 77 K. We decompose the data into two-dimensional decay-associated spectra (2D DAS) to reveal the excitation and detection dependent spectral signatures associated with energy and charge transfer within the PSII RC. We interpret the 2D DAS in the context of an exciton model and proposed pathways for charge separation. The 2D DAS reveal a high degree of variation in the kinetics as a function of excitation wavelength. We observe rapid ~50-150 fs energy equilibration throughout the PSII RC and a heterogeneous distribution of rates associated with charge transfer, ranging from ~1-3 ps. We observe 6-8 ps energy transfer from states absorbing near 670 nm, as well as ~40-60 ps processes consistent with secondary charge transfer from a radical pair intermediate or charge transfer from a trap state.

Effects of chirp on two-dimensional Fourier transform electronic spectra

Sun, 13 Jun 2010 22:02:21 -0400

Patrick F. Tekavec, Jeffrey A. Myers, Kristin L. M. Lewis, Franklin D. Fuller and Jennifer P. Ogilvie, Optics Express, (2010) 18, 11, 11015-11024.

We examine the effect that pulse chirp has on the shape of two-dimensional electronic spectra through calculations and experiments. For the calculations we use a model two electronic level system with a solvent interaction represented by a simple Gaussian correlation function and compare the resulting spectra to experiments carried out on an organic dye molecule (Rhodamine 800). Both calculations and experiments show that
distortions due to chirp are most significant when the pulses used in the experiment have different amounts of chirp, introducing peak shape asymmetry that could be interpreted as spectrally dependent relaxation. When all pulses have similar chirp the distortions are reduced but still affect the anti-diagonal symmetry of the peak shapes and introduce negative features that could be interpreted as excited state absorption.

Multidimensional electronic and vibrational spectroscopy: an ultrafast probe of molecular relaxation and reaction dynamics

Sun, 1 Nov 2009 00:11:26 -0400

Jennifer P. Ogilvie and Kevin J. Kubarych, Advances in atomic, molecular, and optical physics, (2009) 57, 249-321.

Multidimensional optical spectroscopy in the visible and infra- red is a rapidly developing technique enabling direct observation of complex dynamics of molecules in complex environments such as liquids and proteins. Measuring the correlation between excited and detected frequencies with sub-picosecond resolution has enabled the resolution of long-standing problems such as energy transfer in photosynthesis and the life- sustaining structural rearrangements of liquid water. This chapter aims to provide a bridge between the concepts familiar in the AMO physics community and how those ideas and experi- mental methods are applied to condensed phase molecular spectroscopy. We outline the technical challenges of these powerful methods while considering a few examples of experi- ments that showcase the unique perspective offered by 2D electronic and vibrational spectroscopy.

Two-dimensional electronic spectroscopy with a continuum probe

Thu, 23 Apr 2009 22:10:11 -0400

Patrick F. Tekavec, Jeffrey A. Myers, Kristin L. M. Lewis, and Jennifer P. Ogilvie, Optics Letters, (2009) 34, 9, 1390-1392.

We report 2D Fourier transform electronic spectroscopy obtained in the pump–probe
geometry using a continuum probe. An acousto-optic pulse shaper placed in the pump arm of a standard pump-continuum probe experiment permits 2D spectroscopy that probes a broad spectral range. We demonstrate the method on a simple dye system exhibiting vibrational wavepacket dynamics that modulate the peak shapes of the 2D spectra. The broad spectral range of the continuum probe allows us to observe vibronic cross peaks in the 2D spectra.

Comparing coherent and spontaneous Raman scattering under biological imaging conditions

Mon, 9 Mar 2009 21:50:53 -0400

Meng Cui, Brandon R. Bachler, and Jennifer P. Ogilvie, Optics Letters, (2009) 34, 6, 773-775.

We compare imaging based on coherent and spontaneous Raman scattering (SpRS) under conditions relevant for biological imaging. Using a broadband laser source, we perform spectral domain imaging of polystyrene beads using coherent Stokes Raman scattering and SpRS and ﬁnd comparable signal levels. Short interaction lengths, low molecule number, and low incident power all reduce the advantages available with coherent Raman methods. We present calculations to support our measurements.

Chemical imaging with Fourier transform coherent anti-Stokes Raman scattering microscopy

Fri, 24 Oct 2008 22:29:48 -0400

Meng Cui, Joshua Skodack, and Jennifer P. Ogilvie, Applied Optics, (2008) 47, 31, 5790-5798.

We report chemical imaging using Fourier transform coherent anti-Stokes Raman scattering (FTCARS) microscopy. Adding a passively phase-stable local field to amplify the weak FTCARS signal, we also demonstrate interferometric FTCARS microscopy, permitting reduced incident power to be used for imaging. We discuss signal-to-noise considerations and the conditions necessary to effectively suppress background noise, allowing FTCARS microscopy that is limited by the shot noise of the detector. We also
discuss differences between the signal-to-noise obtainable by time and frequency domain coherent anti-Stokes Raman scattering (CARS) methods.

Two-color two-dimensional Fourier transform electronic spectroscopy with a pulse-shaper

Wed, 15 Oct 2008 22:16:28 -0400

Jeffrey A. Myers, Kristin L. M. Lewis, Patrick F. Tekavec and Jennifer P. Ogilvie, Optics Express, (2008) 16, 22, 17420-17428.

We report two-color two-dimensional Fourier transform electronic spectroscopy obtained using an acousto-optic pulse-shaper in a pump-probe geometry. The two-color setup will facilitate the study of energy transfer between electronic transitions that are widely separated in energy. We demonstrate the method at visible wavelengths on the laser dye
LDS750 in acetonitrile. We discuss phase-cycling and polarization schemes to optimize the signal-to-noise ratio in the pump-probe geometry. We also demonstrate that phase-cycling can be used to separate rephasing and nonrephasing signal components.

Time-delayed coherent Raman Spectroscopy

Tue, 1 Jan 2008 23:11:05 -0500

J. P. Ogilvie, M. Cui,D. Pestov, A. Sokolov, M. O. Scully
Molecular Physics, (2008) 106, 2, 587-594.

Incoherent Raman spectroscopy is a widely used tool in physical and chemical science. Coherent Raman spectroscopy, e.g. CARS (coherent anti-Stokes Raman scattering) on the other hand has not been as widely adopted. One reason for this is the well-known ‘nonresonant background’ originating from both solvent and target molecules, due to the instantaneous electronic response and multiple off-resonant vibrational modes. However, with the advent of short and ultrashort pulsed lasers the CARS technique is now being applied to microscopy and the detection of anthrax-type endospores via various extensions of coherent spectroscopy. With such applications in mind, a simple physical picture of CARS spectroscopy is presented, having much in common with Dicke superradiance. Recent work is discussed that provides an effective method for mitigation of the background noise.

Interferometric Fourier transform coherent anti-Stokes Raman Scattering

Fri, 1 Sep 2006 23:51:16 -0400

Meng Cui, Manuel Joffre, Joshua Skodack, and Jennifer P. Ogilvie Optics Express, Vol. 14, Issue 18, pp. 8448-8458 (2006).

We present an interferometric time-domain Fourier transform implementation of coherent anti-Stokes Raman scattering (CARS). Based on a single femtosecond laser source, the method provides a straight-forward scheme for obtaining high resolution CARS spectra. We give a theoretical description of the method, and demonstrate good agreement between simulation and experimental CARS spectra. We also discuss the method’s relation to other CARS approaches for microscopy and microspectroscopy applications.

Fourier-transform coherent anti-Stokes Raman scattering microscopy

Wed, 15 Feb 2006 23:56:15 -0500

Jennifer P. Ogilvie, Emmanuel Beaurepaire, Antigoni Alexandrou, and Manuel Joffre Optics Letters, (2006) 31, 4, 480-482.

We report a novel Fourier-transform-based implementation of coherent anti-Stokes Raman scattering (CARS) microscopy. The method employs a single femtosecond laser source and a Michelson interferometer to create two pulse replicas that are fed into a scanning multiphoton microscope. By varying the time delay between the pulses, we time-resolve the CARS signal, permitting easy removal of the nonresonant back- ground while providing high resolution, spectrally resolved images of CARS modes over the laser bandwidth (1500 cm−1). We demonstrate the method by imaging polystyrene beads in solvent.

Use of coherent control for selective two-photon fluorescence microscopy in live organisms

Sat, 14 Jan 2006 00:03:02 -0500

Jennifer P. Ogilvie, Delphine Débarre, Xavier Solinas, Jean-Louis Martin, Emmanuel Beaurepaire and Manuel Joffre Optics Express, (2006) 14, 2, 759-766.

We demonstrate selective fluorescence excitation of specific molecular species in live organisms by using coherent control of two-photon excitation. We have acquired quasi-simultaneous images in live fluorescently-labeled Drosophila embryos by rapid switching between appropriate pulse shapes. Linear combinations of these images demonstrate that a high degree of fluorophore selectivity is attainable through phase- shaping. Broadband phase-shaped excitation opens up new possibilities for single-laser, multiplex, in-vivo fluorescence microscopy.

Determination of the Fe-CO bond energy in myoglobin using heterodyne-detected transient thermal phase grating spectroscopy

Sat, 18 Jun 2005 00:22:58 -0400

M. Walther, V. Raicu, J. P. Ogilvie, R. Phillips, R. Kluger, R. J. D. Miller J. Phys. Chem. B, (2005) 109, 20605-20611.

The bond energies at active sites of proteins are intimately coupled to the structure-function relationship in biological systems. Due to the unknown nature of the protein relaxation along a reaction coordinate, it has not been possible to directly determine bond energies relevant to protein function. By embedding proteins in trehalose glasses, it is possible to freeze out protein relaxation on short time scales and determine the bond energies of photolabile ligands using photothermal spectroscopies. As a prototypical example, the photo- dissociation dynamics and energetics of carboxy-myoglobin (MbCO) in a trehalose glass matrix at room temperature were studied by transient absorption (or pump-probe) and transient thermal phase grating spectroscopy to determine the CO recombination dynamics and associated energetics, respectively. Both the initial energetics of the bond breaking and the energy released upon bond reformation could be used, on a time scale faster than significant protein relaxation, to determine the Fe-CO bond energy as 34 ( 4 kcal/ mol. This bond energy is significantly larger than that typically cited (25 kcal/mol) on the basis of indirect measurements but is in good agreement with recent theoretical predictions (35 kcal/mol) (Rovira, C.; Parrinello, M. Int. J. Quantum Chem. 2000, 80, 1172). This result in combination with the theoretical study suggests that protein structure plays a significant role in the bond energies at active sites which in turn provides a tuning element of the effective barrier heights independent to the transition state region.

Fourier transform measurement of two-photon excitation spectra: applications to microscopy and optimal control

Fri, 15 Apr 2005 00:17:25 -0400

Jennifer P. Ogilvie, Kevin J. Kubarych, Antigoni Alexandrou, and Manuel Joffre, Optics Letters, (2005) 30, 911-913.

We report a novel Fourier transform method for measuring two-photon excitation spectra. We demonstrate this method using simple dye molecules and discuss its applications in two-photon fluorescence microscopy and optimal control. This method facilitates an intuitive interpretation of recent control experiments in terms of tuning the nonlinear spectrum of the exciting laser source.

CO vibration as a probe of ligand dissociation and transfer in myoglobin

Fri, 2 Jul 2004 22:01:45 -0400

T. Polack, J. P. Ogilvie, S. Franzen, M. Vos, M. Joffre, J.-L. Martin, A. Alexandrou,
Physical Review Letters, (2004) 93, 018102.

We report femtosecond visible pump, midinfrared probe, spectrally integrated experiments resolving the dynamics of CO in myoglobin upon photodissociation. Our results show a progressive change in absorption strength of the CO vibrational transition during its transfer from the heme to the docking site, whereas the vibrational frequency change is faster than our time resolution. A phenomenological model gives good qualitative agreement with our data for a time constant of 400 fs for the change in oscillator strength. Density-functional calculations demonstrate that indeed vibrational frequency and absorption strength are not linearly coupled and that the absorption strength varies in a slower manner due to charge transfer from the heme iron to CO.

Two-dimensional spectroscopy using diffractive optics based phase-locked photon echoes

Sat, 7 Feb 2004 22:04:39 -0500

M. Cowan, J. P. Ogilvie, R. J. D. Miller, Chemical Physics Letters, (2004) 36, 184-189.
A novel technique has been developed to passively phase-lock heterodyne-detected three-pulse photon echo experiments for two- dimensional optical spectroscopy. By using a diffractive optic to generate the pulses required, and with careful introduction of the time delays between the pulses, we achieve excellent passive phase-locking, approaching k=100 at a wavelength of 540 nm. The ability to generate phase-locked pulse pairs with independent time delays solves a long standing impediment for stable phase sensitive detection in true optical analogues of multi-dimensional nuclear magnetic resonance (NMR) techniques, and should be equally valuable in executing related multi-dimensional spectroscopies in the infrared.

Observation of the Cascaded Atomic to Global Length Scales Driving Protein Motion

Wed, 9 Apr 2003 22:07:59 -0400

M. Armstrong, J. P. Ogilvie, M. Cowan, A. Nagy and R. J. D. Miller, Proceedings of the National Academy of Sciences USA, (2003) 100, 4990-4994.

Model studies of the ligand photodissociation process of carboxy- myoglobin have been conducted by using amplified few-cycle laser pulses short enough in duration (<10 fs) to capture the phase of the induced nuclear motions. The reaction-driven modes are ob- served directly in real time and depict the pathway by which energy liberated in the localized reaction site is efficiently channeled to functionally relevant mesoscale motions of the protein.

The dynamics of ligand escape in MbCO: Q-band transient absorption and four-wave mixing studies

Sat, 22 Jun 2002 22:21:52 -0400

J. P. Ogilvie, M. Plazanet, G. Dadusc and R. J. D. Miller, Journal of Physical Chemistry B, (2002) 106 10460-10467.
The dynamics of ligand escape from carboxymyoglobin are studied via Q-band transient absorption and diffractive optics-based four-wave mixing. The latter approach provides an interferometric method for following protein motions and energetics and allows unambiguous assignment of different signal components to specific dynamical processes, a problem that has hindered all photothermal, photoacoustic, and grating methods in the past. In particular, the real part of the four-wave mixing signal is isolated, and it is demonstrated that the excited-state population contribution to the signal can be identified and removed by tuning the probe to wavelengths where this contribution vanishes (“zero-crossings”). At these probe wavelengths, changes in the real part of the index of refraction are small compared to those of the imaginary part, making the heterodyne measurement sensitive to errors in setting the phase of the reference field. We solve this problem with a new balanced detection method that isolates the real part of the signal and is extremely robust against phase errors. The location of the zero-crossings in the population contribution to the index of refraction is found to be complicated by the presence of spectral shifts in the transient absorption that can be characterized and removed with a time-dependent Kramers-Kronig analysis. The spectral shifts are most apparent near the isosbestic points and show similar dynamics to the four-wave mixing signal, suggesting that both are sensitive to the same dynamical processes. These dynamics were observed previously by using four-wave mixing with an off-resonant probe and were assigned to CO migration out of the protein via a number of discrete channels. It appears that both the photoinduced protein conformational relaxation and CO migration through the protein contribute to the transient absorption signal, making the two effects difficult to separate. The direct coupling of the protein motions to the index of refraction changes in the four-wave mixing experiments aids in distinguishing the two processes.

Myoglobin dynamics: evidence for a hybrid solid/fluid state of matter

Fri, 1 Jun 2001 22:25:35 -0400

J. P. Ogilvie, M. Armstrong, M. Plazanet, R. J. D. Miller, (2001), Journal of Luminescence 94-95, 489-492.

Diffractive optics-based heterodyne-detected four-wave mixing signals of protein motion: From “protein quakes” to ligand escape for myoglobin

Tue, 22 May 2001 22:54:50 -0400

G. Dadusc, J. Ogilvie, P. Schulenberg, U. Marvet, R.J.D. Miller, Proceedings of the National Academy of Sciences USA, (2001) 98, 6116-6120.

Ligand transport through myoglobin (Mb) has been observed by using optically heterodyne-detected transient grating spectroscopy. Experimental implementation using diffractive optics has provided unprecedented sensitivity for the study of protein motions by enabling the passive phase locking of the four beams that constitute the experiment, and an unambiguous separation of the Real and Imaginary parts of the signal. Ligand photodissociation of carboxymyoglobin (MbCO) induces a sequence of events involving the relaxation of the protein structure to accommodate ligand escape. These motions show up in the Real part of the signal. The ligand (CO) transport process involves an initial, small amplitude, change in volume, reflecting the transit time of the ligand through the protein, followed by a significantly larger volume change with ligand escape to the surrounding water. The latter process is well described by a single exponential process of 725 +- 15 ns at room temperature. The overall dynamics provide a distinctive signature that can be understood in the context of segmental protein fluctuations that aid ligand escape via a few specific cavities, and they suggest the existence of discrete escape pathways.

Advances in grating-based photoacoustic spectroscopy for the study of protein dynamics

Sun, 1 Feb 1998 22:12:47 -0500

G. Dadusc, G. Goodno, H. L. Chiu, J. Ogilvie , R.J.D. Miller, (1998), Israel Journal of Chemistry, 38, 191-206.