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The collection by confocal Raman microspectrometry in the motorized point-by-point scanning mode of crystalline samples with heterogeneity larger than the spatial resolution (~1 μm) generates large amounts of useable Raman spectral data. The present selected examples of fine, medium, and coarse crystal powders (anhydrite, CaSO4; calcite, CaCO3; gypsum, CaSO4·2H2O; and (NH4)2SO4) treated by the new Simplisma method combining conventional and second derivative data demonstrate the main role of the crystal size on the number and shape of the resolved spectra. With fine crystal powders (size less than 0.5 μm), well-known powder Raman spectrum characteristics of each compound were extracted. These spectra were often superimposed on a weak baseline. With medium and coarse crystal powders (size more than 1 μm), several significant spectra were extracted for each pure crystalline compound. These spectra were found to be analogous to the polarized spectra previously obtained with oriented large single crystal and were attributed to the several scattering contributions according to the symmetry of the several vibrational modes. The band splittings by the static and dynamic crystal effects can be resolved by the Simplisma approach using the pure variable concept according to the width of the splitting depending on the crystal. These results were explained by theoretical equations deduced from the Raman tensor elements and orientational functions of the crystal-fixed coordinates with respect to the space-fixed coordinates. These findings could provide accurate assignment of the resolved spectra extracted by the Simplisma approach from mixtures with large heterogeneities and can provide meaningful applications to Raman imaging of environmental and material samples.

The UV laser flash photolysis (248 nm, 10 ns) of biphenyl (BP) occluded in void space of aluminum rich faujasitic X zeolites Nan(AlO2)n(SiO2)192-n with n = 85, 96 has been investigated by diffuse reflectance transient UV−visible absorption (DRTUV) and time-resolved resonance Raman (TR³) measurements on the nano- and microsecond time scales. TR³ measurements were carried out using an 8 ns probe pulse at 370 nm. Delays between pump and probe pulses (50 ns to 100 μs) provide evidence of triplet state BP(T1), radical cation BP^•+, and radical anion BP^•- with planar quinoidal structures. Self-modeling mixture analysis (SIMPLISMA) of DRTUV data sets resolved pure absorption spectra of BP(T1), BP^•+, BP^•-, and trapped electron as Na4³⁺. Data processing determines also the decays of the corresponding concentrations between 0.5 and 340 μs for loading values corresponding to 1, 2, 4, and 8 BP per unit cell. All the decays of specific concentration were found to fit a model of dispersed heterogeneous kinetics. At lower laser fluence, BP(T1) was found to be the major transient species for all the loading values. Lifetime mean values of BP(T1) were found to be 40 and 110 μs at low and high loading, respectively. Photoionization was found to be dominant at higher pump laser fluence. At low loading, Na4³⁺ cluster and BP^•+ are produced in high yield with relatively different lifetimes, 10 μs and ~500 μs, respectively. The recombination process includes probably supplementary electron transfers with the zeolite framework. At high loading, BP^•- (20 μs) concomitantly forms BP^•+ (12 μs) as a result of photoejected electron capture by BP(S0). The most important role of porous solids with large pores such as X faujasite with respect to photophysical and photochemical BP behaviors in solution appears to be the efficient trapping of photoejected electron in the solid network.

The predictions of the sorption energy, sorption site, conformation, mobility, and vibrational spectra of biphenyl (BP, C12H10) occluded in nonacidic faujasitic Y zeolites Mn(SiO2)192-n(AlO2)n (MnFAU, n = 0 or 56 and M = Na⁺, K⁺, or Cs⁺) were carried out using Monte Carlo simulations (MC), molecular mechanics (MM), and molecular dynamics (MD) calculations. The zeolite−biphenyl interactions have been tuned by varying the aluminum content n, the charge-balancing cation M⁺ of the zeolite, and the BP loading. No preferential sorption site was expected in purely siliceous FAU at 300 K, whereas well-defined location sites energetically favored were expected in M56FAU aluminated faujasite. BP lies in the cavity in a twisted conformation with one phenyl group facially coordinated to the SII cations and the other phenyl group engaged in the 12-ring windows. The accommodation of two BPs within the same supercage occurs at relatively low coverage (2 BP/UC) and is hindered by the M⁺ size. The diffuse reflectance UV−visible absorption data indicate the occupancy of 2 BP per supercage at bulk loading higher than 1 BP/UC. Surprisingly, the BP mean-square displacements (MSD) was found to be slightly lower in FAU than in Na56FAU, although the intracage mobility was found to be higher, while the BP MSD was found to be lower with bulky M⁺ cations. The calculated vibrational densities of states of the atoms of the framework, M⁺ and BP, were found to be in reasonable agreement with the frequency values deduced from the IR absorption and Raman scattering spectra of BP-loaded MnFAU, bare MnFAU, and free BP. These results indicate no marked constraint between host and guest even at high BP coverage. The BP rapid motions average the microenvironments and vibrational couplings as found in solution. The experimental conditions of the BP sorption and the Ar, He, or O2 gas pressure do not induce significant changes of occluded BP characteristics.

Significant Raman and infrared spectra of the fully dehydrated and bare hexagonal M20EMT zeolites (M = Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, NH4⁺, and H⁺) have been obtained particularly in the low-frequency region, at room and low temperature. The vibrational properties of M20EMT were found to be analogous to those of cubic M40FAU with identical aluminum content. However, significant changes in position and intensity of the bands assigned to the framework vibrations were observed according to the nature of the extraframework charge-balancing cation of the exchanged zeolites. Molecular dynamics calculations were used to model the vibrational features of the MnEMT (n = 0 or 20; M = Na⁺ or K⁺) framework and extraframework cations. The main features of both the IR and Raman spectra were reproduced in the mid as well as in the low-frequency ranges. The results of the calculations demonstrate that the cation vibrations significantly participate in the spectral range from 20 to 250 cm^-1 for all cation sites and are in accurate agreement with the infrared and Raman features assigned to the cation motions. The data of the molecular dynamics simulations of the window fluctuations in the MnEMT zeolites show that the aluminum content and extraframework cations affect both the size and the amplitude of the fluctuations of the windows in the zeolite, although the cations are not located in the windows. The calculated spectral densities of the window fluctuations show the most prominent peaks around 100 cm^-1 and are in agreement with the low-frequency Raman features observed around 100 cm^-1.

Polarized Raman spectra of the reference materials carbon tetrachloride and α-quartz are obtained with the Raman microprobe MOLE with the use of different high-numerical-aperture objectives. The depolarization ratios of the Raman bands of isotropic samples are in good agreement with those obtained with the use of conventional instruments, provided that the reflection or transmission factor of the beamsplitter is introduced as a correction. Even with the very wide-aperture objectives used, the depolarization effect is not large and can be evaluated theoretically. Correct polarized spectra of anisotropic samples can also be obtained with a Raman microspectrometer. Here again, the depolarization effect induced by the wide-aperture objective is not large and can be evaluated theoretically if the birefringence of the crystal does not play a significant role. The depolarization induced by the birefringence is especially important when incident and scattered light propagate in a direction close to the optical axis of the crystal, but can be minimized by a reduction of the optical path within the sample.