Time-resolved infrared absorption

A kinetic trace for a particular metal carbonyl intermediate is recorded at a specific wavelength obtained from the time-resolved infrared absorption spectrum. Suitable data analysis allows determination of the kinetics of the decay of the intermediate. 

The IR spectra of carbazole and carbazole-(H20) ( =l-3) clusters in a supersonic jet, measured by IR dip spectroscopy, show vibrational structures of both the monomer and the clusters in the 2900-3800 cm frequency region, assigned to the NH stretch of carbazole and the OH stretches of H2O molecules in the clusters <2001PCA8651>. In the first excited singlet and triplet states A -(4-cyanophenyl)carbazole gives rise to transient bands at 2090 cm and 2060 cm detected by time-resolved infrared absorption spectroscopy and attributed to the CN stretch modes of the molecule <2002CL340>. 

The C=0 group of coumarin (98, R = CH3) is a potential hydrogen bond acceptor. By using subpicosecond time-resolved infrared absorption spectroscopy, following photoexcitation of the cumarin chromophore of 98, in its complex with aniline, the hydrogen bond dissociation rate is in the order of femtoseconds and the aniline reorients itself by reformation of the hydrogen bond with a new geometry166. 

The kinetics of the reaction of NO with methyl radicals in the presence of acetone as the bath-gas was studied by Jodkowski et al,212 using time-resolved infrared absorption spectroscopy. The kinetics of CH3 + NO was studied under pseudo-first-order conditions, i.e. with [NO] [CH3], while the contribution from the self-reaction of methyl radicals... 

Fig. 10.29 Time-resolved infrared absorption data for a probe wavelength of 4.63 pm, following photoexcitation (400 nm) of the N3 Ru dye anchored on different oxide surfaces. (Duration of pump laser pulse, 100 fs). (After ref. [53])...

Figure 15. Time resolved infrared absorption spectra of Vs(N02) in 940 nm thick PVN films during shock loading, in reflectance units. Calculated plots include only thin film interference effects, excluding pressure and temperature shifts and chemical reaction, making the differences between the experimental and calculated spectra the primary subjects of interest. Shock pressures were determined by interferometry. Arrows show the time at which the shock has fully traversed the film and rarefaction begins.

A. Yamakata, T. Ishibashi, H. Onishi, Kinetics of the photocatal3dic watersplitting reaction on Ti02 and Pl/Ti02 studied by time-resolved infrared absorption spectroscopy . Journal of Molecular Catalysis A Chemical, 199, 85-94, (2003). 

Pt/Ti02 photocatalyst exposed to methanol vapor studied with time-resolved infrared absorption spectroscopy, 106 (2002) 9122-9125. 

Millisecond Time-Resolved Infrared Absorption Measurements... 

For microsecond to nanosecond time-resolved infrared absorption measurements, three types of spectroscopic methods have been developed (i) a method using an infrared laser, (ii) a method using a dispersive spectrometer, and (iii) a method using an FT-IR spectrometer. The time resolution of each of these is limited to the fastest time-response capability of the detector used. 

In ultrafast, time-resolved infrared absorption measurements by the pump-probe method, the sample is first excited by an ultrashort pump pulse, and then irradiated by an ultrashort infrared pulse (probe pulse) after a certain delay time from the excitation by the pump pulse. The delay time of the probe pulse from the pump pulse is usually changed by the difference in the optical path lengths of the pump and probe pulses (a delay time of 1 ps arises from a path difference of about 0.3 mm). When the infrared spectrum of a molecule in an excited electronic state is measured, pulses in the ultraviolet to visible region are used for the pump purpose, and pulses in the infrared region are used for the probe purpose. When a vibrationally excited molecule is the target of such a measurement, pulses in the infrared region are used for both the pump and probe purposes. The transient (or time-resolved) infrared absorption spectra by this method are usually measured as the difference in absorption intensities for the probe pulses between the measurements with the pump pulses and those without the pump pulses. 

Picosecond to femtosecond time-resolved infrared absorption measurements were initiated in the middle of the 1980s. In 1984, Heilweil et al. [17] studied the dynamics of vibrational relaxation by using picosecond infrared pulses obtained from an OPA (LiNb03) excited by a mode-locked Nd YAG laser. 

Since about the end of the 1990s, generation of ultrashort pulses has become easier due to the progress of laser technology, and, as a consequence, a measuring method based on femtosecond Ti sapphire regenerative amplifier with a kilohertz repetition rate has become the mainstream of fast time-resolved infrared absorption measurements. 

Sakamoto, A., Nakamura, O., Yoshimoto, G. and Tasumi, M. (2000) Picosecond time-resolved infrared absorption studies on the photoexcited states of poly(p-phenylenevinylene). J. Phys. Chem. A, 104,4198-4202. 

Sakamoto, A. and Takezawa, M. (2009) Picosecond time-resolved infrared absorption study on photoexcited dynamics of regioregular poly(3-hexylthiophene). Synth. Met., 159, 809-812. 

Taatjes, C. A. (1999). Time-resolved infrared absorption measurements of product formation in Cl atom reactions with alkenes and alkynes. Int. Rev. Phys. Chem. 18,419. 

J. C. Bolinger, T. J. Bixby, and P. J. Reid,/. Chem. Phys., 123,084503 (2005). Time-Resolved Infrared Absorption Studies of the Solvent-Dependent Vibrational Relaxation Dynamics of Chlorine Dioxide. 

Reports of new tungsten complexes include the reaction of the transient species W(CO)5(cyclohexane) with cyclo-C4H 0 (n = 4, 6, 8) studied by time-resolved infrared absorption spectroscopy. Schultz and co-workers have noted an unusual solvent isotope effect in the reaction of W(CO)5(solv) (solv = cyclohexane or cyclohexane-rfu) with TFIF. Some interesting chemistry involving W(CO)5(2,5-dihydrofuran) is noted by the same group. Adducts of cyclotriphosphorus complexes have been reported by Di Vaira and co-workers, leading to the synthesis, solid state structure and solution behaviour of the bis-adducts [ (MeC(CH2PPh2)3)Co (P3)(M(CO)5 2], where M is a Group 6 metal. 

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