Step-scan FTIR spectroscopy

Although very detailed, fundamental information is available from ultrafast TRIR methods, significant expertise in femtosecond/picosecond spectroscopy is required to conduct such experiments. TRIR spectroscopy on the nanosecond or slower timescale is a more straightforward experiment. Here, mainly two alternatives exist step-scan FTIR spectroscopy and conventional pump-probe dispersive TRIR spectroscopy, each with their own strengths and weaknesses. Commercial instruments for each of these approaches are currently available. 

IR and Raman spectra of copper(II) complexes of histamine gave evidence for the formation of [Cu2(L H)2]2+, CuL2 and CuL2+ at high pH, Cu(LH)2, CuL2- and CuL2+ at lower pH all with coordination through the imidazole moiety.251 Time-resolved step-scan FTIR spectroscopy was used to probe the... 

Rammelsberg, R., Boulas, S., Chorongiewski, H. and Gerwert, K. (1999) Set-up for time-resolved step-scan FTIR spectroscopy of noncyclic reactions. Vih. Spectrosc., 19, 143-149. 

To obtain IR spectra on a time scale of nanoseconds, the sample cell in conventional spectrometers is usually excited by an Nd YAG laser. Flow cells with a pathlength of at least 0.1 mm must be used for photoreactive samples and the pulse repetition frequency is then limited to 1 Hz. In step scan FTIR spectroscopy,211 the time evolution is collected at single points of the interferogram, which is then reconstructed point-by-point and subsequently transformed to time-resolved IR spectra. Alternatively, dispersive instruments equipped with a strong IR source can be used.212 The time resolution of both methods is about 50 ns. FTIR instruments provide a triggerable fast-scan mode to collect a complete spectrum within a few milliseconds.213... 

Time-resolved infrared spectroscopy (TRIR) has been outstandingly successful in identifying reactive intermediates and excited states of both metal carbonyl [68,69] and organic complexes in solution [70-72]. Some time ago, the potential of TRIR for the elucidation of photochemical reactions in SCFs was demonstrated [73]. TRIR is particularly suited to probe metal carbonyl reactions in SCFs because v(CO) IR bands are relatively narrow so that several different species can be easily detected. Until now, TRIR measurements have largely been performed using tunable IR lasers as the IR source and this has restricted the application of TRIR to the specialist laboratory [68]. However, recent developments in step-scan FTIR spectroscopy promise to open up TRIR to the wider scientific community [74]. 

Turro, George, and co-workers [70] have also observed and studied an acyl radical in solution by TRIR methods in their investigation of the photochemistry of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (Scheme 2.4). More recently, Vasenkov and Frei [71, 72] reported the generation of the acetyl radical by photolysis of 1-naphthyl acetate (Scheme 2.5) or pinacolone (Scheme 2.2 R = Me, R = f-Bu) in zeolite NaY. Through the use of step-scan FTIR spectroscopy, they observed a carbonyl stretching mode at 2125 cm , interestingly... 

Experimentation with step-scan interferometry in electrochemistry began in the early 1990s (cf Ref. [23]), and interest has grown steadily ]24, 29-31, 51-54]. Step-scan FTIR spectroscopy provides a means to investigate time- and frequency-dependent processes. Measurements are hmited to reversible systems. However, a great deal of insight can be gained into the molecular transformations that accompany the external perturbation [181-183]. 

Although we have focused on the photochemistry of Rh(Cp )(CO)2 (Cp =Cp or Cp ) so far, the most complete understanding of C-H reactions came in parallel TRIR studies on Rh(Tp )(CO>2 (Tp = HB(3,5 -Me2pyrazol-l-yl)3, and extensive reviews cover this work." We choose this example since this investigation built upon matrix-isolation and liquid Xe studies. A combination of ultrafast TRIR and ns-step-scan FTIR spectroscopy was used to unravel the mechanism of alkane C-H activation by Rh(Tp An alkane complex was formed within the earliest... 

Over recent years, internal reflectance infrared studies have tended to concentrate on the study of relatively thick films of conducting polymers or layers, (see, for example, the work of Pham and coworkers [49, 50], or Kvarn-strom, Nauer, Neugebauer and coworkers [51-54]) in which sensitivity was not a particular problem, or on the semiconductor-electrolyte interface, (see the work of Chazalviel and coworkers [35, 40, 41]), in which the SPP excitation approach is not appropriate. However, interest has focused again on this phenomenon with the surface-enhanced infrared absorption spectroscopy (SEIRAS) studies of Osawa and coworkers [19, 26, 27, 46, 55, 56], who have combined the application of the Kretschmann configuration with step-scan FTIR spectroscopy to study fast, reversible electrochemical processes on timescales down to microseconds [26, 46, 57-60]. 

Journal of Polymer Science Polymer Physics Edition 31, No. 12, Nov. 1993, p.l769-77 DYNAMIC RHEO-OPTICAL CHARACTERISATION OF A LOW DENSITY POLYETHYLENE/PERDEUTERATED HIGH DENSITY POLYETHYLENE BLEND BY TWO DIMENSIONAL STEP-SCAN FTIR SPECTROSCOPY... 

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