Population inversion, definition

The lineshape factor C =.94 for a Gaussian line. When the measured data of Jj//o are reduced by the use of Eq. (85), the plots of An versus t in Fig. 30 are obtained. The plot shows the unexpected result that the population inversion continues to increase after termination of the flash. This behavior is consistent with the observation of several authors that additional chemical pumping processes are operative in the system 44-45>, although no definite conclusion on their nature has yet been reached. It can be seen that under the conditions of Fig. 30 the pumping contribution of this reaction is comparable to that of the photodissociation. 

The fact that the molecule only exhibits a stable existence in its excited state benefits the laser because the repulsive, dissociative ground state does not allow population to accumulate it is by definition empty. This means that every excited molecule contributes to the population inversion. Furthermore, no absorption of generated laser light by molecules in the ground state can occur, as is the case for most other types of laser there is only spontaneous and stimulated emission. As a consequence, excimer lasers exhibit very high laser gain but, because of the nature of the chemical production process of the excited molecule, only pulse operation is realized in commercial systems. 

For more details, see p. 300. Copper atoms in a large excess of argon mixed with NF3 in a flow system produce a flame which is green at the bottom and blue at the top. The emission spectrum contains a variety of molecular bands belonging to CuF (C,B,A- X) and lines of atomic Cu (12% of the total emission). The photon yield (for the definition, see the AI+NF3 reaction) was measured to be 0.1% at 5Torr. Population inversion was observed between some of the Cu-atom states, and this was explained by a mechanism similar to that in the AI+NF3 reaction [6, 15, 16]. 

The i"C chemical shift thus reveals the relative configuration of substituents in molecules with a definite conformation, e.g. the axial position of the OH group in trans-3-methylcyclohexanol, cis-4-methylcyclohexanol, -D-arabinofuranose and a-D-xylopy-ranose (Table 2.12). It turns out, in addition, that these compounds also take on the conformations shown in Table 2.12 (arabinopyranose, C the others, CJ if they occurred as the other conformers, then the OH groups on C-l in these molecules would be equatorial with the result that larger shifts for C-l, C-3 and C-5 would be recorded. A ring inversion (50 50 population of both conformers) would result in an average C shift. 

Fig. 1-7. A definition sketch for the proposed upscaling scheme depicting (a) gamma distribution of central pore lengths with % = 2, and hypothetical six bins (note the inverse relationships between 3 and 1.) (b) three different filling stages in the population of unit cells (represented by l. l.fl) defined at three chemical potential values to g (dry-wet) and (e) the rcNtdllng hypothetical characteristic curve.

Another physiological characteristic of animals that is frequently measured is the upper lethal temperature. The definition of this temperature is somewhat arbitrary, and the values quoted for a given animal are thus widely spread. Assuming that the upper lethal temperature depends only upon temperature, it would seem that the upper lethal temperature could be defined by extrapolation of a time (for a given fraction of population to die) versus temperature relation from high temperatures, until time and temperature became independent. In other words, above the lethal temperature, time and temperature would be approximately inversely proportional below, no relation would be evident. 

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