CC BY
16'22
ALT' LD-1-14
LASER DIAGNOSTICS AND SPECTROSCOPY
Broadband two-dimensional spectrochronography with ultrashort pulses in the mid-infrared
E.A. Stepanov, A.N. Zhdanov, I.V. Savitskii, G.D. Ivanov, A.A. Lanin, A.B. Fedotov, A.M. Zheltikov
Lomonosov Moscow State University, Leninskie Gory 1, stroenie 2, 119991 Moscow, Russia; e-mail: a.b.fedotov@physics.msu.ru, zheltikov@physics.msu.ru
The methods of 2D Fourier-transform infrared (2D-FTIR) spectroscopy are most widely used to analyze the dynamics of complex organic compounds, in particular, new types of molecular markers used in the analysis of biological complexes [1 - 6]. Two-dimensional IR spectroscopy makes it possible to obtain information about the environment of proteins reflected in a two-dimensional line shape, to measure the characteristic times of excitation transfer from one vibrational mode to another, to distinguish between solvent affected and disordered proteins, and to increase the spectral resolution due to the so-called off-diagonal peaks. For example, using 2D-FTIR spectroscopy, new features of the relationship between the vibrational degrees of freedom in nucleic acids were discovered [7 - 9]. The high temporal resolution of the technique allows analyzing the dynamics of peptide folding and protein oligomerization [8 - 11], including the technique of labelling cells with the carbon-13 isotope [11].
In this work, we present a universal laser platform for broadband 2D spectroscopy using ultrashort mid-IR pulses. The laser system developed for 2D spectroscopy generates radiation pulses with a duration of less than 70 fs and a wavelength tunable in the range of 2.6 - 10 mm. Broadband excitation and probing by pulses with such parameters, in combination with the heterodyne detection technique implemented in the mid-IR range, open up possibilities for studying ultrafast dynamics of molecular coherence, as well as ultrafast population kinetics and energy exchange between different degrees of freedom in a wide class of complex molecular systems (fig. 1).
Figure 1. (Left) Schematic of a two-dimensional IR spectrometer; (right) two-dimensional IR spectrum of dicobalt
octacarbonyl measured for a delay t2 = 8 ps.
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