Metrological Applications of Ellipsometry with Temperature Change

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Matrix effect on triatomic CO₂ molecule: Comparison between krypton and xenon.

Vibrational energies for low-lying levels of CO2 trapped in rare gas matrices are determined for four isotopic species by applying a theoretical model allowing contact transformation method to be applied as perturbation technique to the molecule trapped in a distorted lattice structure. Results are given for molecules trapped in krypton and xenon. For the latter, both face-centered-cubic (fcc) and hexagonal-closed-packed (hcp) structures are shown to be possible. New harmonic and anharmonic constants are determined that allows calculation of matrix dependent calculated energy levels. It is shown that if distortion of the lattice is calculated for one isopotomer, then it can be used to calculate vibrational energies of other trapped isotopic species. Changes are more significant for harmonic potential constants than for third order anharmonic ones. Calculated energy levels compare well with observed ones. Predictions of unobserved ones for the latter isotope and other species are also made. The values calculated for 13C16O2 are consistent with LIF experimental results

Three-dimensional imaging in a diffusive medium using crossed correlation by frequency summation

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Thermal spin transition in [Fe(NH2-trz)3]Br2 investigated by spectroscopic ellipsometry

We investigated the thermal hysteresis of a pelleted sample of the spin-crossover compound [Fe(NH2-trz)3]Br2 by means of spectroscopic ellipsometry, in the temperature range 264–358 K. The ellipsometric parameters (psi,Delta) have been recorded in the optical range 240–1000 nm. The corresponding absorption and dispersion spectra show temperature-invariant isobestic points located at 240 and 291 nm, respectively. We found that the high-spin-fraction data, derived from the integrated absorption curves, are in excellent agreement with the magnetic data recorded on the same sample. We also investigated the consistency of the optical data by application of the Kramers-Kronig relations, which are well obeyed above ~450 nm. All these results demonstrate that the spectroscopic ellipsometry is well adapted to characterize the spin-crossover transition. We also expect that this nondestructive technique will be highly relevant to investigate the physical properties of thin films of switchable molecular solids, involving a change in the electronic properties upon a thermally or photoinduced phase transition