Synthetic and experimental spectra

The overall aggreement between the synthetic and experimental spectra is remarkably good, providing support for the stated assumption. Slight discrepancies between the synthetic and real spectra may be attributed to changes in absorptivity of some of the bands with pH, which were ignored in this simple analysis. 

Figure 4. Comparison of synthetic and experimental spectra of a monomeric solution (0.08 M) of CgAO at Z equal 0.5.

Figure lib. Comparison of the CH stretching region of synthetic and experimental spectra of 0.40 M Ct2AO at Z equal 0... 

Comparison with experimental showed very good quality of the predicted intensities as well as of the underlying ab initio DMSs. An illustration of the quality of the intensities presented in this work is given in Fig. 20, where the synthetic and experimental spectra T = 296 K) are compared. 

Kinetic Modeling. For all the synthetic heme complexes studied, the lifetime of the first intermediate AS was on the order of 250 fs in agreement with the femtosecond study of Martin et al. ( ). As the jitter in the pulse duration is on the order of 1 ps, the AS lifetime is very approximate and chosen to obtain the best fit to the experimental spectra. 

Fig. 11. High-resolution 29Si MAS NMR spectra of synthetic zeolites Na-X and Na-Y at 79.80 MHz (58). Experimental spectra are given in the left-hand columns Si(nAl) signals are identified by the n above the peaks. Computer-simulated spectra based on Gaussian peak shapes and corresponding with each experimental spectrum are given in the right-hand columns. Individual deconvoluted peaks are drawn in dotted lines.

Spectroscopic Probes of Cavitation Conditions. Determination of the temperatures reached in a cavitating bubble has remained a difficult experimental problem. As a spectroscopic probe of the cavitation event, MBSL provides a solution. High resolution MBSL spectra from silicone oil under Ar have been reported and analyzed (7). The observed emission comes from excited state C2 and has been modeled with synthetic spectra as a function of rotational and vibrational temperatures, as shown in Figure 7. From comparison of synthetic to observed spectra, the effective cavitation temperature is 5050 =L 150 K. The excellence of the match between the observed MBSL and the synthetic spectra provides definitive proof that the sonoluminescence event is a thermal, chemiluminescence process. The agreement between this spectroscopic determination of the cavitation temperature and that made by comparative rate thermometry of sonochemical reactions is surprisingly dose (6). 

Figure 8. Comparison of the o, CH2 frequencies of CgAO from experimental spectra of 0.08 M and 0.40 M solutions, and synthetic micelle-only spectra.

The optical spectra of natural and synthetic transition metal-doped corundums have been extensively studied both theoretically and experimentally. Data reviewed elsewhere (Bums and Bums, 1984a Bums, 1985a) are summarized in table 5.2. The Ae and CFSE values are only approximate because the ground-state splittings, 6, of the tlg orbital group (cf. fig. 2.9) are unknown but could amount to 1,000 cm-1 for some cations in corundum. 

Zhao, B., Rong, Y.-Z., Huang, X.-H., Shen, J.-S. Experimental and theoretical study on the structure and electronic spectra of imiquimod and its synthetic intermediates. Bioorg Med Chem Lett 17 (2007) 4942-4946. 

Experimental evidence for the vibrational structure of XHX transition states has been provided by photoelectron spectroscopy of XHX- anions with X = Cl, Br, and I (134,160-163). This technique, by inducing photodetachment of an electron from the XHX" anions, probes the Franck-Condon region, which is believed for these systems to include geometries in the vicinity of the transition state region for the neutral systems. Spectral bands have been interpreted as evidence for trapped-state resonances associated with asymmetric stretch-excited levels of the transition state (160-163), and they are in general agreement with synthetic photoelectron spectra calculated from the scattering computations of Schatz (17-19). In recent experimental spectra (158,162), more closely spaced oscillations have been observed these are apparently related to rotational thresholds as described by Schatz. 

Spectral prediction is required especially in the case of characterization and structure elucidation of large complex molecnles, such as natural products [30], A complete one-to-one correspondence for the assignment of the peaks in the spectra is not possible from the experimental spectra. Prediction is also required in the case of mechanistic nnderstanding for synthetic organic chemistiy. Many methods have been developed to predict spectrum, given stmctural information. 

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