Photoelectric action

A. Campetti31 concludes from his experiments that in darkened unsaturated sodium vapour, freed from the electrons emitted from the surface of the fused metal, ionization takes place spontaneously and that the absorption of the ZMine is strictly related to the conductivity of the vapour. Further, when absorption is observed in sodium vapour below 400°, it is probably the result of electrons from the surface of the fused metal, or from a photoelectric action on the atoms of sodium vapour. The emitting or absorbing vibrations in sodium vapour with respect to the D-line are those of positive-ion-atoms. 

All photoeffects involve the absorption of photons to produce an excited state in the absorber or liberate electrons directly. With the direct release of electrons, photoemission may occur from the surface of solids. While the excited state may revert to the ground state, it may proceed further to a photochemical reaction to provide an electron-hole pair (exciton) as the primary photoproduct. The exciton may dissociate into at least one free carrier, the other generally remaining localized. In an externally applied electric field, photoconduction occurs. Photomagnetic effects arise in a magnetic field. Absorption of photons yield photoelectric action spectra which resemble optical absorption spectra. Photoeffects are involved in many biological systems in which charge transfer takes place (e.g., as observed in the chlorophylls and carotenoids) [14]. 

In view of the experimental uncertainties involved in determining Ic and Ac the above estimate for Eg is too close to the optical absorption threshold ( 2 eV) (11,12) to argue a priori that the dominant polymer absorption be not a transition between valence and conduction band of the conjugated polymer chain. Photoelectric action spectra were necessary to disregard this possibility. Results... 

The action of light on yellow arsenic has been described on p. 29 the rate of change is not affected by radium rays. When placed in the light from a mercury lamp, arsenic exhibits a photoelectric effect, emitting electrons the longest effective wavelength is A 2360. At 1100° to 1150° C. a resonance series is excited in the vapour of arsenic 1 by each of the mercury lines AA 2483, 2536, 2654 and 2804 the fundamental frequency is apparently 410 cm.-1, which gives as the distance As to As in the diatomic molecules 1-94 A., or 77 per cent, of the distance in crystalline arsenic (see p. 35). 

Sommerfeld applied the theory of quanta to the emission of X- and y-rays, to the photoelectric effect, and sketched the theory of the ionization potential. At the beginning of his paper he discussed in some detail the relationship observed in the emission of X- (or y-) rays by cathode (or 0) rays and arrived at the conclusion that large quantities of energy are emitted in shorter times and small quantities of energy in larger times. 9 According to Sommerfeld this empirical result speaks in favor of the central role played in atomic and molecular phenomena by the quantum of action h introduced by Planck, the dimensions of which are energy multiplied by time. 

General Properties of Uranium Compounds— I ranous and Uranyl Salts— Influence of Light on Uranium Compounds—Photoelectric Cells—Eleetro-chemioal Behaviour—Physiological Action—Uses. 

I. The Problem,—When electrons are ejected from the K orbits of atoms in the target of an X-ray tube, the question arises Are most of them ejected by direct action of the cathode rays through their repulsive forces or are they ejected by an indirect process, the photoelectric effect of continuous-spectrum X-rays excited by the cathode rays or perhaps, do both processes occur often From the experimental standpoint, this question takes the form Are the characteristic rays from the target of a tube mostly direct primary rays, or are they mostly indirect primary rays (really a restricted class of secondary rays), or are they a mixture of comparable amounts of both classes ... 

Interestingly, the action spectrum of self-sensitization follows the photoelectric gain curve of the multilayers It was therefore concluded that the same transition... 

Roller (29) deposited caesium on a silver surface, to give a multimolecular layer, and then exposed the composite surface to the action of oxygen. Simultaneous observations of the photoelectric properties of the Cs-CsgO-Ag surface showed that as fast as caesium oxide was formed it was covered by a polyatomic layer by processes of readjustment by diffusion in... 

J. J. Thomson was able to show that the negative electric charge that leaves the zinc plate under the influence of ultraviolet light consists of electrons. The emission of electrons by action of ultraviolet light or x-rays is called the photoelectric effect. The electrons that are given off by the metal plate are called photoelectrons they are not different in character from other electrons. 

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