Heat mode laser recording

In addition to heat emission, radiative decay processes may also occur, in which light is emitted due to a transition from the lowest excited singlet or triplet state to the ground state (fluorescence or phosphorescence). In order to effect rapid and efficient conversion of optical energy (the laser) to heat, dyes which exhibit low fluorescence and in which excitation primarily involves the singlet states are the most suitable for heat-mode recording.196... 

The quantities a, c, f, F, r, and p are the thermal diffusivity, sound speed, heat capacity ratio, bulk viscosity coefficient, shear viscosity coefficient, and density of the sample, respectively and Eo, a, P and Cp are the energy fluence of the laser beam, the optical absorption coefficient, the volume expansion coefficient, and the isobaric heat capacity, respectively, of the fluid. Tlie first and second terms in Eq. 2 describe the time dependences of the thermal and acoustic modes of wave motion, respectively. Since the decays of the acoustic and thermal mode densities back to their ambient values take place on such different time scales (microsecond time scale for acoustic mode and millisecond time scale for thermal mode), they were recorded on the oscilloscope using different time bases. 

Raman spectra can be recorded in times as short as several nanoseconds using pulsed laser excitation/gated array detection techniques. This capability is important for the identification of transient species during fast chemical reactions or for characterizing structural failure modes in thin films exposed to heat or intense electromagnetic fields. An existing system... 

In this context, dialdehyde la (5 mg, 0.017 mmol), sarcosine (14 mg, 0.157 mmol) and five-fold excess of Ceo (60 mg, 0.083 mmol) dissolved in 10 ml of o-dichlorobenzene (o-DCB) heated at 130 °C for 90 min. After a typical work up procedure, the reaction mixture is purified by recycling HPLC on a preparative Buckyprep Cosmosil column (250 X 20 mm, toluene eluent, lOml/min flow rate) to furnish bis-fullerene derivative 3 in 32 % yield. The bis-fullerene 3 shows moderate solubility, thus allowed us to record and NMR spectra (Supp. Info., Fig. SI) corroborating the depicted structure in Scheme 1. The attenuated-total-reflectance infra-red (ATR-IR) spectrum of 3 demonstrates the characteristic stretching vibrations of the C-H (2803-3030cm" ) as well as the characteristic absorptions for fullerenes (Supp. Info., Fig. S2). Matrix-assisted-laser-desorption time-of-flight mass-spectroscopy (MALDI-TOF-MS), in the negative ionization mode and with the aid of trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile shows the molecu-... 

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