Time resolved FTIR

Pibel C D, Sirota E, Brenner J and Dai H L 1998 Nanosecond time-resolved FTIR emission spectroscopy monitoring the energy distribution of highly vibrationally excited molecules during collisional deactivation J. Chem. Phys. 108 1297-300... 

Leone S R 1989 Time-resolved FTIR emission studies of molecular photofragmentation Accounts Chem. Res. 22 139-44... 

The kinetics of intercalation have been followed by FTIR and QCM gravimetry. For example, the frequency change of a QCM with a 20-layer CdAr film (exposed to H2S) was followed as a function of immersion time in a CdCl2 solution (Fig. 3.5.5) (46). The percent conversion [calculated from mass of film on QCM and stoichiometry in Eq. (3) reaches 100% within about 100 min immersion. In contrast, time-resolved FTIR spectra of CdBe/H2S and HgBe/H2S films immersed into Cd2+ and Hg2+ solutions, respectively, indicated that the intercalation of metal ions into the LB film of BeH takes 24-48 h to complete (21). The kinetics of the sulfidation reaction [Eq. (4) are discussed in a later section. 

The chapter is set out in the following way. Section II contains elements of the theory of Fourier transformations which, rather than being exhaustive (and exhausting), aims to cover the details and limitations of the technique which are of importance for the experimentalist to understand. Section III contains descriptions and comparisons of the SS and CS methods and outlines the advantages and pitfalls of each, together with recommendations for their suitability for specific applications. Section IV presents recent results from time-resolved FTIR emission experiments, emphasizing photochemical applications. 

III. A PRACTICAL GUIDE TO TIME-RESOLVED FTIR EMISSION STUDIES... 

In this section it is hoped to provide useful experimental details which demonstrate the simplicity of both the time-resolved FTIR technique and its incorporation into an experiment. Two major implementations of the technique have emerged, namely stopped and continuous-scan they are dealt with separately below in Sections III.A and III.B. A detailed comparison of the two methods is then presented in Section III.C. 

Figure 1. Schematic diagram of the Michelson stop-scan interferometer used for time-resolved FTIR emission studies. Reproduced with permission from Ref. 38.

The following sections are not intended to give an exhaustive account of the application of time-resolved FTIR emission spectroscopy, but highlight particular problem areas in chemical physics to which the technique is particularly suited and focus on photochemical reactions, and results which have emerged since the previous reviews on the subject [26,27]. 

Very recently the formation and vibrational relaxation of OH(X2n , v = 1-9) by 02 and C02 [73] and NH(X3 -, v = 1-3) by N2, Ar, and H2 [72] has been investigated in electron-irradiated gas mixtures. OH( )-m)-1,d-2) and NH(d-n) —1) IR emission was observed using a quasi-SS time-resolved FTIR spectrometer, averaging about 100 samples to characterize the IR transient for each of 1000 sampling positions. Time-dependent populations are shown for OH(t = 1-6) in Figure 24, taken from... 

Sloan and co-workers have used their CS time-resolved FTIR spectrometer to determine rates of formation and subsequent V -+ T and V - V relaxation of OH(u ) [45,163]. In one study vibrationally excited OH in v = 1-4 was generated by the reaction... 

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