Photoelectric action effect

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]. 

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. 

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 ... 

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. 

Inductance, eddy current, hall effect, photoelectric, capacitance, etc. Robust noncontact switching action The digital outputs are often directly fed to the digital controller... 

For both n and p-type SBSCs the net result of this action is an accumulation of opposite charge on either side of the junction causing it to become forward biassed. For n-type SBSCs the metal becomes positively charged with respect to the semiconductor and for p-type SBSCs the metal becomes negatively charged. In both cases the emf may be used to dissipate power in an external electrical load. This effect is known as the photoelectric effect. 

Immediately following the invention of optical lasers in the early 1960s, all instruments used lasers as the light source. Acquisition of spectra from samples with arbitrarily high Rayleigh radiation required some spectrometer developments as well as implementation of low-noise detectors. Curiously, the physics on which both laser and photomultiplier operation are based is derived from work of Albert Einstein. Photomultipliers operate by using the photoelectric effect for which Einstein received the Nobel Prize for work done in 1905. Laser action was a demonstration of stimulated emission that was predicted by Einstein in 1917. A discussion of laser action will not be included in this chapter, but the reader can refer to a text on optoelectronics such as Ref. 17. 

The kinetics of photopotential was studied by Liu and Mauzerall , who explained the decay by a rate constant that exponentially decreases with the distance between the pigment cation and ferricyanide. The other conclusion from their study is that the pigment cation does not transverse the BLM in less than 10 msec. To examine the action spectra of pigmented BLM, a technique known as photoelectrospectrometry has been developed, which is based on the photoelectric effect and optical spectroscopy . 

Electrophysiological techniques, in particular, patch-clamp, may be difficult to use with microorganisms, the dimensions of which vary from a few hundreds to a few pm. They are the only techniques (with the exception of some special fluorescent probes, like ion-specific fluorescent indicators), however, that allow photoelectric effects, like light-induced membrane depolarizations, action potentials, and photic receptor potentials, to be measured. Then, these data can be related to Hght-induced modification of the motor (flagella and cilia) activity. "... 

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