Cesium vapor pressure

Fi(i. 13. Distribution of thermionic electron emission of a tungsten-monocrystal wire in cesium vapor in the [Oil] zone at A 2,000°, B 900°, C 850°K. Cesium vapor pressure corresponds to room temperature [according to Johnson and Shockley (35)]. 

It is one of four metals — mercury, cesium, and rubidium — which can be liquid near room temperature and, thus, can be used in high-temperature thermometers. It has one of the longest liquid ranges of any metal and has a low vapor pressure even at high temperatures. 

Liquid Metals. If operating temperatures rise above 250—300°C, where many organic fluids decompose and water exerts high vapor pressure, hquid metals have found some use, eg, mercury for limited appHcation in turbines sodium, especially its low melting eutectic with 23 wt % potassium, as a hydrauhc fluid and coolant in nuclear reactors and potassium, mbidium, cesium, and gallium in some special uses. 

Achener, P. Y., 1964, The Determination of the Latent Heat of Vaporization, Vapor Pressure, Enthalpy, and Density of Liquid Rubidium and Cesium up to 1,800°F, Proc. 1963 High Temperature Liquid Metal Heat Transfer Technology Meeting, Vol. 1, pp. 3-25 USAEC Rep. ORNL-3605. (2) Achener, P. Y, 1965, The Determination of the Latent Heat of Vaporization, Vapor Pressure of Potassium from 1,000-1,900°F, Aerojet-General Nucleonics Rep. AGN-8141. (2)... 

Bonilla, C. F., D. L. Sawhuey, and N. M. Makansi, 1962, Vapor Pressure of Alkali Metals III, Rubidium, Cesium, and Sodium-Potassium alloy up to 100 psia, Proc. 1962 High Temperature Liquid MetaI Heat Transfer Tech. Meeting, BNL-756, Brookhaven, NY. (3)... 

Fig. 1. Mean reduced vapor pressure curve for the halides of sodium, potassium, rubidium, and cesium. Average deviation from the mean is shown by the vertical lines.

Sorokin and Lankard illuminated cesium and rubidium vapors with light pulses from a dye laser pumped by a ruby giant-pulse laser, and obtained two-step excitation of Csj and Rbj molecules (which are always present in about 1 % concentration at atomic vapor pressures of 10" - 1 torr) jhe upper excited state is a repulsive one and dissociates into one excited atom and one ground-state atom. The resulting population inversion in the Ip level of Cs and the 6p level of Rb enables laser imission at 3.095 jum in helium-buffered cesium vapor and at 2.254 pm and 2.293 /zm in rubidium vapor. Measurements of line shape and frequency shift of the atomic... 

This vapor pressure can be deduced from kinetic theory and the rate of arrival of Cs atoms per square centimeter per second (3,4). This arrival rate. A, can be calculated from the measured value of the saturation positive ion current. Langmuir first showed that if the tungsten is hot enough every cesium atom that strikes the surface evaporates off as a positive ion of cesium. This saturated positive ion current, i.p, can be measured easily with a medium sensitive galvanometer when the collector is negative. It is related to A by the equation... 

Suppose the vapor pressure is adjusted so that the arrival rate. A, is about 2.6 X 10 cesium atoms/cm.Vsec. If the temperature of the tungsten filament is about 550°K., the surface will be covered with more... 

Cs (g). Vapor pressure data were reported by Hackspill,1 Kroner,1 Scott,1 and Langmuir and Kingdom.1 See also Boer and Dippel,1 van Laar 9 and Egerton 3 The values for the energy states of gaseous monatomic cesium are from Fowler,3 Miller and Laporte,1 and Bacher and Goudsmit.1... 

Vanadium oxytrichloride is a lemon-yellow liquid. Its boiling point is 124.5°C. at 736 mm. and 127.16°C. at 760 mm. It remains liquid at —77°. The vapor pressure at —77° is 4.1 mm. at 0°, 21 mm. and at 85°C., 270 mm. Its density in grams per milliliter is 1.854 at 0° and 1.811 at 32°C. At ordinary temperatures, it neither dissolves nor reacts with carbon, hydrogen, nitrogen, oxygen, silicon, tellurium, or metals except the alkali metals and antimony. The reactions with the alkali metals are explosive at characteristic temperatures, varying from 30°C. for cesium to 180°C. for sodium (lithium not determined). Small... 

The main disadvantage of this detector is that its performance deteriorates with time. Reese [8] examined the performance of the NPD in great detail. The alkali salt employed as the bead is usually a silicate and Reese demonstrated that the loss in response was due to water vapor from the burning hydrogen converting the alkali silicate to the hydroxide and free silica. Unfortunately, at the normal operating temperature of the bead, the alkali hydroxide has a significant vapor pressure and consequently, the rubidium or cesium is... 

Cesium hydroxide (cesium hydrate [CAS 21351-79-1]) Corrosive (see p 157). Highly irritating upon direct contact severe burns may result. Dusts are irritating to eyes and respiratory tract. 2 mg/m Colorless or yellow crystals that absorb moisture. Negligible vapor pressure. 

The converter enclosure is hermetically sealed so that the atmosphere between the electrodes can be controlled. In the conventional thermionic converter, the interelectrode space is filled with cesium vapor from a liquid reservoir at a pressure of 1 torr. The cesium performs two functions. First, it adsorbs on the electrodes to provide the desired electron emission properties. Second, it provides positive ions to neutralize the electron space charge so that practical current densities can be obtained from the converter. 

The adsorption of a fractional layer of an electronegative element, such as oxygen, will increase the work function of the surface. However, Langmuir and his co-workers found that, when such a surface is operated in cesium vapor, the work function (for a given cesium pressure and substrate temperature) may be significantly lower than without the electronegative additive. The thermionic converter performance can be improved by a lower collector work function or a lower cesium pressure in the interelectrode space (or both). 

The difference between the two embodiments concerns the relation of the mean free path of the electrons to the distance of the electrodes in the cell. In the modification which has been described in most detail by Hemquist, Kanefsky, and Norman at RCA (13) [but was considered even before by Hatsopoulos, Kaye, Nottingham (14j 15j 18, 19) and by V. Wilson (16, 17), the vapor pressure of cesium is so low that the mean free path of the electrons exceeds the distance between the hot and cold electrodes in the tube. Electromotive forces up to 2.5 have b n obtained from a single cell and thermal efficiencies up to 10%. The electric power per cm of hot surface was of the order of 10 to 20 w—a very respectable figure. The second approach has been described in most detail by Grover and his collaborators at Los Alamos (20, 21). In their system, the mean free path of the electrons is smaller than the... 

The original system for generation and wick feed of cesium vapors is employed. Cesium vapor is rejected into space through the controlled throttle. Depending on cesium flow rate, the necessary pressure is settled in the volume of interelectrode gaps. Cesium is heated by the liquid metal loop. 

The thermally induced redistribution of the tellurium and selenium isotopes shown under certain conditions might be due to the formation of cesium telluride and selenide both compounds exhibit comparatively high vapor pressures (10- MPa at 1000 K, 0.1 MPa at 2000 K). 

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