The 4000 Å transition of crystal anthracene

New low temperature determinations of ε{lunate}(ω) for crystal anthracene locate the 0-0 transition origin at 25096 ± 6 cm for the b-polarization. There is no Stokes shift of the fluorescence origin. The exciton bands which are optically accessible by probing the (ab) crystal face with normal incidence light polarized either parallel or perpendicular to the b-axis have a temperature dependent splitting. The Davydov splitting at 77°K is 267 ± 12 cm. The temperature dependence of the k = 0 polariton splitting and the exciton bandwidths (b-polarization and a-polarization) are also given and together with the Davydov splitting provide a test of the adequacy of theories of exciton interactions. The polarization ratio measured as the ratio of the oscillator strengths of the two transitions (f/f) is quite temperature dependent for both the region of the (0-0) transition and over the total vibronic transition. At 77°K, the value of f/f is 8.0 for the origin region close to that expected of an oriented gas but is 4.5 over the total transition. Some spectral structure observed only in the b-polarized reflectance spectrum at temperatures less than 77°K is related to the existence of defects localized near the surface

Exciton dynamics in molecular crystals from line shape analysis. The use of spectral moments and correlation functions

A method for elucidating exciton dynamics from the profile of ωε{lunate}i(ω) is developed and illustrated by using anthracene crystal reflectance data. From the Green's function for the exciton-phonon system, terms contributing to each spectral moment are rendered explicit. The Green's function is related to certain correlation functions which together with the spectral moments are evaluated from the spectral data

Optical parameters from reflectance data. A new and versatile approach

A method is described which can replace both a Kramers‐Kronig and a dispersion analysis as a means of obtaining optical parameters from reflectance data of condensed systems. It has advantages whenever a large number of data points must be sampled and when the absorption band profile is used to interpret quasiparticle dynamics. The efficiency of the method arises because evaluation of the phase shift upon reflection is better performed by multiplication in the time domain than by convolution in the frequency domain as is done by a Kramers‐Kronig method. The efficiency of the method is illustrated and using reflectivity data of an anthracene crystal, the errors in its use, while still comparable to the less efficient traditional methods are shown to be insignificant compared with the experimental errors in such data. Copyrigh

Polarization energies and quasi-free electron states of rare gas crystals

Crystal polarization energies are calculated at several temperatures for Xe, Kr, Ar and Ne and at several pressures for He. These results are used to estimate energies of the quasi-free electron state from spectroscopic data for Xe, Kr, and Ar

SMALL AMPLITUDE COLLECTIVE PROTON MOTIONS IN WATER NETWORKS - APPLICATION TO ICES, CLATHRATES AND AQUEOUS SOLUTIONS

Une caractéristique de la spectroscopie Raman de l'eau en relation avec le mouvement collectif de petite amplitude des protons, est employée pour étudier la structure de réseau de l'eau liquide, des glaces, semiclathrates, alcools, electrolytes et des mélanges H2O/H2O2.A feature in the Raman spectrum of water networks, assigned to small amplitude collective proton motions, is used to probe the network structure in ices, liquid water, H2O/H2O2 mixtures, semiclathrates, alcohols and electrolytes

In-situ imaging of particle size distribution in an industrial-scale calcination reactor using micro-focusing particle shadowgraphy

Abstract not availableShipu Han, Zhiwei Sun, Claire de Jacobi du Vallon, Tim Collins, Matthew Boot-Handford, Mark G. Sceats, Zhao Feng Tian, Graham J. Natha