Time-Resolved Temperature-Jump Infrared Spectroscopy at a High Repetition Rate

Abstract

Time-resolved temperature-jump infrared absorption spectroscopy at a 0.5 to 1 kHz repetition rate is presented. A 1 kHz neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pumping an optical parametric oscillator provided >70 µJ, 3.75 µm pump pulses, which delivered a temperature jump via excitation of the O–D stretch of a D2O solution. A 10 kHz train of mid-infrared probe pulses was used to monitor spectral changes following the temperature jump. Calibration with trifluoroacetic acid solution showed that a temperature jump of 10 K lasting for tens of microseconds was achieved, sufficient to observe fast processes in functionally relevant biomolecular mechanisms. Modeling of heating profiles across ≤10 µm path length cells and subsequent cooling dynamics are used to describe the initial <100 ns cooling at the window surface and subsequent, >10 µs cooling dynamics of the bulk solution.

Combining steady state and temperature jump IR spectroscopy to investigate the allosteric effects of ligand binding to dsDNA

“…The discrepancy is due to the competing effects of DNA melting and cooling occurring in the T-jump measurement, which occur on similar timescales. 27,37 For example; at T 0 À T m = À5 1C, the non-equilibrium T-jump measurement captures around 40% of the full change in absorbance observed in both AT and GC marker modes when measured under equilibrium conditions at this temperature (Fig. 3(a and b)).…”

“…The T-jump pump, mid-IR probe spectrometer used for DNA melting experiments has been described previously along with T-jump calibration methods and identical procedures were followed. 27,37 T-jump excitation pulses were produced at a repetition rate of 1 kHz using a home-built Nd:YAG-pumped optical parametric oscillator (OPO). The B4 ns-duration pulses produced had a maximum energy of 70 mJ at 2660 cm À1 , resonant with the high frequency wing of the OD stretching vibration of D 2 O, enabling a T-jump of B9 1C while avoiding complete absorption of the pump radiation by the solvent.…”

“…The pulse duration and center frequency of the mid-IR pulses were 50 fs and 1630 cm À1 respectively; the latter was coincident with the characteristic base vibrational modes of dsDNA. The difference between the 10 kHz repetition rate of the Ti:sapphire laser and the 0.5 kHz repetition rate of the T-jump pump pulses, combined with the use of an electronic delay to control the relative pulse timings of the pump and probe laser systems, enabled collection of T-jump pump-IR probe spectra at time delays (t pp ) from 1 ns to 2 ms. 37…”

“…Subtracting equilibrium IR absorption spectra at a temperature, T 0 , from that obtained at T 0 + 10 1C (equivalent to the T-jump achieved by the non-equilibrium experiment 27,37 ) provides a measurement of the change in absorbance of each marker mode of the dsDNA sample that occurs if the sample is allowed to re-equilibrate at the higher temperature. As all steady state and T-jump IR data were recorded under the same sample conditions (path length and concentration), this is equal to the maximum absorbance change that could be measured in the non-equilibrium experiment.…”

Mode-Selective Vibrational Energy Transfer Dynamics in 1,3,5-Trinitroperhydro-1,3,5-Triazine (RDX) Thin Films

“…This enhanced sensitivity may imply strong coupling between low and high frequency vibrations, supporting a direct energy transfer 4,27 model following a shockwave rather than a "doorway mode"-mediated multiphonon up-pumping scheme. [1][2][3]87,88 To test that specific high frequency reporter vibrational modes are sensitive to long-lived phonon VET, we have recalculated the α-RDX IR spectrum (see Fig. 1) with a 10% static lattice compression to represent some characteristic of the experimental excited phonon bath.…”