Matrix isolation spectra

The advantage of matrix isolation spectroscopy is that it can be performed at low temperature. At the same time no interactions take place between the molecules, and the environment is very vacuum-like. This is confirmed for 1,2,3-triazole for which it was found that the H-2T tautomer is very dominant as was also observed in the gas phase [44] (see later). This is furthermore confirmed by MP2 theoretical calculations performed with the largest 6-311-F-FG(3df,3pd) and augcc-PVTZ basis sets, which suggests that this tautomer is more stable than the less symmetric one by 18 1 kj mol i [45]. 

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Clearly, the effects of ion pair formation in matrix isolation spectra are apparent, particularly in the removal of degeneracy of vibrational modes. However, these can be fit quite well with normal coordinate calculations which show that ion pairing effects cause significant force constant changes. Moreover, it is apparent that the energetics of ion pair formation do provide a limit as to the species which can be studied in this fashion. However, for the species which can be stabilized in this manner, the technique is still effective and provides a model for both ion-molecule reactions and CsF catalysis. 

Figure 5. IR Ar matrix isolation spectra of products from the reaction of Sc atoms with water. Key A, Sc (I255°C) and H O (SJfi) B, Sc (1255°C) and HeO (120ii) C, Sc (1255°C) and H2O(220il) and D, matrix B irradiated for 10 min with K >...

The ground state of ZrO(g) was assumed to be as determined from the matrix isolation spectra of Weltner et al. (2). 

The ground state of ZrO(g) has been determined from the matrix isolation spectra of [65WEL/MCL] to be [85CHA/DAV]. The molecular constants were obtained by [85CHA/DAV] from the data of [55UHL/AKE] and [65WEL/MCL]. From this data, the values determined by [85CHA/DAV] for tbe heat capacity and entropy at 298.15 K of ZrO(g) are ... 

This table lists the fundamental vibrational frequencies of selected three-, four-, and five-atom molecules. Both stable molecules and transient free radicals are included. The data have been taken from evaluated sources. In general, the selected values are based on gas-phase infrared, Raman, or ultraviolet spectra when these were not available, liquid-phase or matrix-isolation spectra were used. 

The matrix-isolated spectra of HNCO, DNCO, HNCS, and DNCS in the far-i.r. (10—50 cm ) and of the CNO anion in the i.r. (550— 5000 cm ) have been recorded. The acid molecules were isolated in both argon and nitrogen matrices at 13 K although no absorptions attributable to the guest molecules were observed in the nitrogen matrix, intense bands were recorded in the argon matrix. These bands are best explained by rotation of the molecule about an axis close to the axis of least inertia. Isotopically enriched cyanate anions have been prepared by direct oxidation reactions and introduced into KCl and KBr single crystals to a maximum concentration of ca. 5 wt. The i.r. spectra of the resultant cyanate ion isotopic species show that these ions are dissolved in the form of a solid solution. 

Most of the assignments for the and E-, modes are consistent with those made previously for biscyclopentadienyl titanium (IV) derivatives (31) in similar matrices, but differs somewhat from the assignments of Balducci et al (30) for the matrix isolated spectra of the biscyclopentadienyl dihalides. Although the E2 modes of the Cp2Tix2 derivatives (where X=F, Cl, Br, I), were previously assigned by Balducci, correlations can not be made with the solid state spectra. Tentative assignments for the E2 mode have therefore been made and are given in Table 3. 

Figure 2 Matrix isolation spectra for a six-component mixture of polycyclic aromatic hydrocarbons (PAHs) lamp excitation at 313nm. P = pyrene, C = chrysene, BbF = benzo[b]fluorene, T=triphenylene, Ph = phenanthrene, BaF = benzo[a]fluorene.

K, and, in this way, the analytes are frozen into a cage of argon molecules, i.e., matrix-isolated. The diameter of the spots is a little larger than that obtained with the DD technique, i.e., 200-300 p,m. Matrix-isolated spectra maydiffer from spectra that have been recorded with conventional methods. In particular, relatively small molecules (MW < 200) may exhibit considerable band-narrowing effects. As a consequence, identification of GC/ MI-FTIR spectra demands special reference collections. 

Transoid, ortho, and gauche conformers of n-Si4Clio Raman and mid-IR matrix-isolation spectra ... 

The final column of Table II shows matrix isolation spectra from Redington and Hamilll and Andrews and Johnson as reassigned by Redington and Hamill.102 The frequencies appear to be highly perturbed and for some reason are closer to the gas-phase harmonic values than the gas-phase anharmonic ones. 

FTIR matrix-isolation spectra were reported for isolated MnOF and MnOF2 species. Raman bands were assigned to MnO modes, associated with Mn02 planes, from spectra of double-layered manganites. ... 

Matrix-isolation spectra cannot be compared to spectra found in libraries of either conventional condensed- or vapor-phase reference spectra. 

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