Photon-heat mode

For any application of photochromic molecules, a discussion of the thermal stability of the colored form is in order. We will discuss two types of photochromic molecules (1) those that operate by a photon-heat mode (photochemical forward reaction and a thermal reverse reaction), such as spiropyran derivatives, and (2) those that exhibit a photon-photon mode, such as diarylethene derivatives. 

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Comparison between heat-mode and photon-mode processes is given in Table I. The main differences are the superior resolution and the possibility of multiplex recording in photon-mode systems. Because of the diffusion of heat, the resolution of heat-mode recording is inferior to that of photon-mode systems. Furthermore, photons are rich in information such as energy, polarization and coherency, which can not be rivalled by heat-mode recording. 

The next stages in the development beyond 20 Gb will be to move away from heat mode recording to photon mode recording. This is discussed elsewhere in this book, under photochromies (Chapter 1, section 1.2.8.3) and under holography, optoelectronics and photonics in Chapter 5. 

The color species developed by near-UV light are hardly affected by irradiation with visible light, suggesting that the back electron transfer is thermal in nature. This is promising for photo-memory, that is, color development by photon-mode and heat-mode bleaching. 

HEAT-MODE AND PHOTON-MODE IMAGE RECORDING (7)... 

Comparisons between heat-mode and photon-mode processes are given in TABLE 1. The main differences are the superior resolution and the possibility of multiplex recording in photon-mode systems. 

Because of the diffusion of heat, the resolution of heat-mode recording is inferior to that of photon-mode systems. 

Furthermore, photons are rich in information such as energy, polarization and coherency, which cannot be rivalled by heat-mode recording. 

TABLE 1. Comparison between heat- and photon-mode image recording. Item Heat-mode Photon-mode... 

LCP is a suitable candidate for this purpose. The merits of photon-mode and heat-mode recording may be combined by the aid of... 

The excited states in Si-based electronics decay by phonons, and thus at DR — 3 mn a huge heat dissipation problem faces nanoscale inorganic electronics. In contrast, molecular devices can also decay from their excited state by photon emission. If the photon decay mode is preferred, then nnimolecular devices will have a great advantage over inorganic ones. 

In a manner similar to that of photorecording materials that are the subject of many studies, photoresponsive gels can be largely divided into two types. They are the photon mode-type, which fimctions by photophysical or photochemical reactions upon irradiation of light, and the heat mode-type, which fimctions by changing photoenergy into thermal energy. 

Enolate anions (4e) that have been heated by infiared multiple photon absorption for which torsional motion about the H2C-C bond, which destabilizes the 7t orbital containing the extra electron, is the mode contributing most to vibration-to-electronic energy transfer and thus to ejection. 

The parameter is the damping constant, and (n) is the mean number of reservoir photons. The quantum theory of damping assumes that the reservoir spectrum is flat, so the mean number of reservoir oscillators (n) = ( (O)bj(O j) = ( (1 / ) — 1) 1 in the yth mode is independent of j. Thus the reservoir oscillators form a thermal system. The case ( ) = 0 corresponds to vacuum fluctuations (zero-temperature heat bath). It is convenient to consider the quantum dynamics of the system (56)-(59) in the interaction picture. Then the master equation for the density operator p is given by... 

Fluxes must be specified during each phase of device operation including startup, heating, burn, fueling, shutdown and failure modes. Plasma failure modes, such as instabilities which cause much of the stored plasma energy to be dumped in a short time may result in large particle or photon fluences to selected small areas of surfaces exposed to the plasma. 

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