Time resolved infrared spectroscopy

Owrutsky J C, Li M, Culver J P, Sarisky M J, Yodh A G and Hochstrasser R M 1993 Vibrational dynamics of condensed phase molecules studied by ultrafast infrared spectroscopy Time Resolved Vibrational Spectroscopy VI (Springer Proc. in Physics 74) ed A Lau (New York Springer) pp 63-7... 

In principle, absorption spectroscopy techniques can be used to characterize radicals. The key issues are the sensitivity of the method, the concentrations of radicals that are produced, and the molar absorptivities of the radicals. High-energy electron beams in pulse radiolysis and ultraviolet-visible (UV-vis) light from lasers can produce relatively high radical concentrations in the 1-10 x 10 M range, and UV-vis spectroscopy is possible with sensitive photomultipliers. A compilation of absorption spectra for radicals contains many examples. Infrared (IR) spectroscopy can be used for select cases, such as carbonyl-containing radicals, but it is less useful than UV-vis spectroscopy. Time-resolved absorption spectroscopy is used for direct kinetic smdies. Dynamic ESR spectroscopy also can be employed for kinetic studies, and this was the most important kinetic method available for reactions... 

Transient terahertz spectroscopy Time-resolved terahertz (THz) spectroscopy (TRTS) has been used to measure the transient photoconductivity of injected electrons in dye-sensitised titanium oxide with subpicosecond time resolution (Beard et al, 2002 Turner et al, 2002). Terahertz probes cover the far-infrared (10-600 cm or 0.3-20 THz) region of the spectrum and measure frequency-dependent photoconductivity. The sample is excited by an ultrafast optical pulse to initiate electron injection and subsequently probed with a THz pulse. In many THz detection schemes, the time-dependent electric field 6 f) of the THz probe pulse is measured by free-space electro-optic sampling (Beard et al, 2002). Both the amplitude and the phase of the electric field can be determined, from which the complex conductivity of the injected electrons can be obtained. Fitting the complex conductivity allows the determination of carrier concentration and mobility. The time evolution of these quantities can be determined by varying the delay time between the optical pump and THz probe pulses. The advantage of this technique is that it provides detailed information on the dynamics of the injected electrons in the semiconductor and complements the time-resolved fluorescence and transient absorption techniques, which often focus on the dynamics of the adsorbates. A similar technique, time-resolved microwave conductivity, has been used to study injection kinetics in dye-sensitised nanocrystalline thin films (Fessenden and Kamat, 1995). However, its time resolution is limited to longer than 1 ns. 

Friedrich Kremer is Professor of Molecular Physics, Materials Research Spectroscopy, Institute of Experimental Physics I, University of Leipzig, Germany. His research interests include broadband dielectric spectroscopy, time-resolved Fourier transform infrared (FTIR) spectroscopy, and experiments with optical tweezers. In 2005 he was awarded with the Karl Heinz Beckurts - Prize in 2011 he received the Wolfgang-Ostwald-Prize from the German Colloid Society. 

The high costs associated with specialist ultrafast laser techniques can make their purchase prohibitive to many university research laboratories. However, centralised national and international research infrastructures hosting a variety of large scale sophisticated laser facilities are available to researchers. In Europe access to these facilities is currently obtained either via successful application to Laser Lab Europe (a European Union Research Initiative) [35] or directly to the research facility. Calls for proposals are launched at least annually and instrument time is allocated to the research on the basis of peer-reviewed evaluation of the proposal. Each facility hosts a variety of exotic techniques, enabling photoactive systems to be probed across a variety of timescales in different dimensions. For example, the STFC Central Laser Facility at the Rutherford Appleton Laboratory (UK) is home to optical tweezers, femtosecond pump-probe spectroscopy, time-resolved stimulated and resonance Raman spectroscopy, time-resolved linear and non-linear infrared transient spectroscopy, to name just a few techniques [36]. 

Recent advances in time-resolved vibrational spectroscopy (time-resolved infrared [TR-IR] and time-resolved resonance raman spectroscopy) have provided further evidence for the description of aryl nitrenium ions as imino-cyclohexadienyl cations. The C-N stretching frequency in singlet diphenylni-trenium ion (generated by LFP of a N-diphenylaminopyridinium salt in acetonitrile) was measured by time-resolved infrared spectroscopy to be v = 1392 cm , which is significantly higher than the v = 1320 cm of diphenylamine. In the UVA is, the diphenylnitrenium ion shows = 425 and 660 nm, with a lifetime X = 1.5 Rs. ... 

Anderson D T, Schwartz R L and Todd M W and Lester M I 1998 Infrared spectroscopy and time-resolved dynamics of the ortho-Hj-OH entrance channel complex J. Chem. Phys. 109 3461-73... 

Dyer R B, Einarsdottir 6, Killough P M, Lopez-Garriga J J and Woodruff W H 1989 Transient binding of photodissociated CO to of eukaryotic cytochrome oxidase at ambient temperature. Direct evidence from time-resolved infrared spectroscopy J. Am. Chem. Soc. Ill 7657-9... 

Yuzawa T, Kate C, George M W and Hamaguchi H O 1994 Nanosecond time-resolved infrared spectroscopy with a dispersive scanning spectrometer Appl. Spectrosc. 48 684-90... 

The potential energy surface [47] for this reaction (Fig. 5) shows many potentially competitive pathways, labeled A-F, leading to the two most exothermic product channels. Many of these pathways can be isotopically separated by reaction of 02 with HCCO in normal abundance, as diagramed in Fig. 5. Zou and Osbom used time-resolved Fourier transform emission spectroscopy to detect the CO and CO2 products of this reaction [47]. Rotationally resolved infrared (IR) spectroscopy can easily identify all the possible isotopologs. For example. Fig. 6 shows a single... 

Time-resolved Fourier transform infrared spectroscopy has been used surprisingly little considering the nuadter of commercial spectrometers that are currently in laboratories and the applicability of this technique to the difficult tine regime from a few is to a few hundred is. One problem with time-resolved Fourier transform spectroscopy and possibly one reason that it has not been more widely used is the stringent reproducibility requirement of the repetitive event in order to avoid artifacts in the spectra( ). When changes occur in the eiaissirr source over the course of a... 

Smith GD, Palmer RA (2002) Fast time-resolved mid-infrared spectroscopy using an interferometer. In Chalmers JM, Griffiths PR (eds) Handbook of vibrational spectroscopy, vol 1. Wiley, Chichester, p 625... 

Yamakata, A., Uchida, T., Kubota, J. and Osawa, M. (2006) Laser-induced potential jump at the electrochemical interface probed by picosecond time-resolved surface-enhanced infrared absorption spectroscopy./. Phys. Chem. B, 110, 6423-6427. 

Samjeske G, Miki A, Ye S, Osawa M. 2006. Mechanistic study of electrocatal3dic oxidation of formic acid at platinum in acidic solution by time-resolved surface-enhanced infrared absorption spectroscopy. J Phys Chem B 110 16559-16566. 

H.W. Biermann, Time-resolved air monitoring using Fourier transform infrared spectroscopy, in Fumigants Environmental Fate, Exposure, and Analysis, ed. J.N. Seiber, J.A. Knuteson, J.E. Woodrow, N.L. Wolfe, M.V. Yates, and S.R. Yates, ACS Symposium Series No. 652, American Chemical Society, Washington, DC, pp. 202-211 (1997). 

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