Ruby fluorescence molecules

Many aryl-substituted pyrylium salts are intensely fluorescent. It is possible to predict these spectral properties by a consideration of the shape of the molecule, the nature of substituents and the length of the ir-electron system (75MI22203). Pyrylium salts have been used as Q-switches for neodymium and ruby lasers in acetonitrile (68MI22200). 

The sample chamber of a DAC is filled with a medium that is able to transfer to the sample a homogeneous pressure, and is transparent in the spectral region of interest. At low temperatures, He, Ne and Xe and also homonu-clear molecules (H2, D2, N2 or O2) have been used as pressure-transmitting media. The hydrostatic behaviour of He and H2 allows experiments at low temperature up to 60 GPa (The kbar unit, traditionally used in many experiments with DACs, is close to 0.1 GPa) and N2 can be used up to 13 GPa. Loading the sample chamber with the sample and the pressure transmitting medium is usually performed by the liquid-immersion technique [40]. Hydrostatic pressure measurements in absorption experiments can be obtained from a calibration of the DAC using the pressure-induced shift of Ri and R2 fluorescence lines of Cr3+of a ruby chip near 694 nm, developed by [8]. However, this calibration is performed at RT and it must be extrapolated at low temperatures. It has been shown by Hsu [16] that the shift of the vibrational lines of the CO2 impurities contained in N2 used for pressure transmission could be used to measure pressure at low temperature. 

Thus, it has been studied azoethane decomposition [21] stimulated by ruby laser (/.=694.3nm) with power density equal to 70+175 MW/cm2. It has been established that the N2 yield is proportional to the order 2.2 0.1 with respect to the light intensity. The authors of [22] suppose that after photon absorption the excited molecules from the first excited singlet state A are transfered to an other excited singlet state B from which fluorescence is forbidden. The both states are at close range. The excited molecules which are on B level may be decomposed with a rate which depends on the nature of radicals linked with azo group. The authors of [23] assume that both mechanisms (thermo-and photo) are identic, but only in the case of photolysis transfer to triplet (T) state is possible. 

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