Time-Dependent IR Spectra

Figure 10.2 Time-dependent IR spectra in the v(CO) range of CpRuH(CO)(PCy3) (compound 1) (0.004mol/L) in the presence of 6 equiv of (CF3)3COH at 220 K in hexane (over a 30-minute period). Compounds 2a to 2c are dihydrogen-bonded complexes, and 3 is a hydrogen-bonded ion pair. (Reproduced with permission from ref. 6.)...

Figure 21.2 (a) Time-dependent IR spectra of a binary solution mixture of OA and ethanol... 

Re(PiPr3)2(NO)(CO)H(H2)]+CF3COO- [7], At smaller CF3COOH concentrations, both molecnles are easily observed together. Under these conditions, by analogy with time-dependent IR experiments, snch NMR spectra will be convenient for time monitoring of the protonation process if a proton transfer is slow on the NMR time scale (the nsual NMR time scale refers to lifetimes between 1 and 10 s). P H NMR spectra will also be appropriate in this context. 

These IR complex index component spectra were used to calculate the spectral effects that would be observed in a shock compression experiment. Figure 12 shows the time-dependent IR reflectance spectra calculated for normal incidence and p polarization in a 1 pm thick PMMA film during passage of the shockwave, assuming no pressure shift of the band frequencies. The uniaxial shock compression ratio fVE = l/(l-Up/us) was 1.5, as expected for... 

Figure 12.21 shows the time-dependent FTIR spectra of PCL melt on an oriented PE substrate at 59 °C with polarized IR beam aligned parallel or perpendicular to the PE chain direction. It is evident that when the polarized IR beam parallels to the chain direction of PE (see Figure 12.21a), the absorbance of conformational bands at 1295, 1245, and 1192cm increases significantly with time. On the... 

Fourier-transform infrared (FTIR) spectrometers encode infrared wavenumbers by moving a mirror in a Michelson interferometer which results in a unique, path-dependent pattern of interference for each light wavelength in the IR beam. FTIRs have come to totally dominate the IR market and are the means by which most of the work described in this review was accomplished. Only for some special applications (modulation spectra and time-dependence studies) are dispersive-based (scanning monochromator or tuned laser) spectrometers still used. The advantages of the FTIR approach are that the entire spectral region of interest can... 

CA 68,61112 (1968) [The authors report on their mathematical analysis of the expl decompn of mixts of H azide with w. From kinetic data and IR spectra of the decompn products a series of reactions were developed to describe the initiation, growth, and completion of the decompn (deton) process. From these reactions the authors derived a series of differential equations based on the variation of the energy of activation with time. They found that the limiting partial pressure of H azide ign is dependent upon the partial pressure of the diluent (w)l... 

Transient IR spectroscopy in the range of the amide I band is a direct tool to follow the structural dynamics of the peptide moiety. IR difference spectra on the bicyclic molecule bc-AMPB are plotted in Fig. 5. Shortly after excitation the absorption is dominated by a red shift. Such a red shift is expected for a strong vibrational excitation of the molecule. On the time-scale of a few picosecond this red shift decays to a large extent and is replaced by a dispersive feature of opposite sign at tD = 20 ps. At later delay times this feature changes details of its shape, it sharpens up and some substructure appears around 1680 cm 1. After 1.7 ns the shape is similar, but not completely identical to the difference spectrum recorded with stationary FTIR spectroscopy. This time dependence shows that the dominant structural change responsible for the IR difference spectrum occurs on the 20 ps time-scale and that minor structural changes continue until nanoseconds and even later times. 

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