Cesium standard

The comb-frequency can be directly compared with the cesium standard. 

The combination of lasers and microwave sources also plays a very important role in metrology. The frequency of 473 THz of the iodine-stabilized HeNe laser at A = 633 nm was measured directly against the cesium standard of time with a chain of lasers and klystrons starting up from a Cs atomic clock. The authors give a total uncertainty of the... 

The Q of a commercial cesium standard is a few parts in 10 . The beam tube is typically <0.5 m in length, and the atoms travel at velocities of > 100 m per second inside the tnbe. This limits the observation time to a few... 

The resonance frequency of hydrogen is much lower than that of cesium, but the resonance width of a hydrogen maser is usually just a few hertz. Therefore, the Q is about 10 , or at least one order of magnitude better than a commercial cesium standard. As a result, the short-term stability is better than a cesium standard for periods out to a few days— typically <1 x 10 (<7yT, at t = 1 sec) and reaching a noise floor of=l x 10 after about 1 hr. However, when measured for more than a few days or weeks, a hydrogen maser might fall below a cesium oscillator s performance. The stability decreases because of changes in the cavity s resonance frequency over time. 

Cesium Dissolve 1.267 g CsCl and dilute to volume. Standardize Pipette 25 ml of final solution... 

Dissolve 1.4148 g RbCl in water. Standardize as described under cesium. Rb (in... 

The determination of cesium in minerals can be accompHshed by x-ray fluorescence spectrometry or for low ranges associated with geochemical exploration, by atomic absorption, using comparative standards. For low levels of cesium in medical research, the proton induced x-ray emission technique has been developed (40). 

Cesium metal is used for time standards based on the natural vibration of the Cs atom, which oscillates 9,192,631,770 times per second, and in high precision oscillators to synchronize fiber optic telecommunication. 

Due to the above requirements, typical optically-transparent materials, such as oxides (glass, quartz, alumina, zirconium oxide etc.) and halides (sodium chloride, lithium fluoride, calcium fluoride, potassium bromide, cesium bromide etc.) are usually unsuitable for use with fluoride melts. Therefore, no standard procedure exists at present for the spectral investigation of fluoride melts, and an original apparatus must be created especially for each particular case. 

Repeating unit of polymer chain including solvation Mn of samples not irradiated based on GPC in NMP with polystyrene standards, or by NMR end-group analysis if so indicated Measured net G value after cesium-137 irradiation corrected relative to Fricke dosimeter... 

The uncorrected magnetic susceptibility of the cesium alum, determined by the Gouy method using the complex HgCo(NCS)4 as standard, is —0.12 c.g.s. units per gram this has been found to change to —0.03 c.g.s. units after 14 weeks.4... 

As a suitable model reaction, the coupling of various substituted carboxylic acids to polymer resins has been investigated by Stadler and Kappe (Scheme 7.8) [28]. The resulting polymer-bound esters served as useful building blocks in a variety of further solid-phase transformations. In a preliminary experiment, benzoic acid was attached to Merrifield resin under microwave conditions within 5 min (Scheme 7.8 a). This functionalization was additionally used to determine the effect of micro-wave irradiation on the cleavage of substrates from polymer supports (see Section 7.1.10). The benzoic acid was quantitatively coupled within 5 min via its cesium salt utilizing standard glassware under atmospheric reflux conditions at 200 °C. 

Gustafson, P.F. 1969. Cesium-137 in freshwater fish during 1954-1965. Pages 249-257 in DJ. Nelson and F.C. Evans (eds.). Symposium on Radioecology. Proceedings of the Second National Symposium. Available as CONF-670503 from The Clearinghouse for Federal Scientific and Technical Information, Natl. Bur. Standards, Springfield, VA 22151. 

Indoleboronic acid 96 was employed by Neel to prepare bis(indolyl)maleimides such as 109 [119]. However, since the standard Suzuki conditions failed (triflate 108 apparently decomposing under the reaction conditions), the use of a phosphine-free Pd catalyst [120] and cesium fluoride [121] was necessary and gave 109 in an acceptable yield of 55%. 

The doso-clusters B Hn2-, B10H102-, and B6H62 are stable entities. Their alkali salts are very water soluble. Cesium as a counter-ion reduces the water solubility considerably, and ammonium ions (especially quaternary ammonium ions) precipitate the cluster anions quantitatively from aqueous solutions. The resulting tri- and tetraalkylammonium salts are usually soluble in organic solvents. This allows chemistry to be performed under conditions which are standard for organic... 

Write a thermochemical equation for the formation of gaseous cesium. The standard enthalpy of formation of Cs(g) is 76.7 kj/mol. 

In 1960 the International Committee of Weights and Measures selected radioactive cesium-137 (with a half-life of about 33 years) as the standard for measuring time. They equated the second with the radiation emitted by a Cs-137 atom that is excited by a small energy source. Thus, the second is now defined as 9,192,631,770 vibrations of the radiation emitted by an atom of Cs-137. There are about 200 atomic clocks around the world that collaborate their efforts to maintain this extremely accurate clock that never needs winding or batteries. 

Cesium is highly reactive. It is the most electropositive metal-more electropositive and reactive than other alkali metals of lower atomic numbers. The standard redox potential E° for the reduction Cs+ -i- e — Cs is -3.026 V. It reacts explosively with water, forming cesium hydroxide, CsOH and hydrogen ... 

Cesium, Cs, and rubidium, Rb, form ideal solutions in the liquid phase, and regular solutions in the solid phase. Their standard state Gibbs free energy changes of melting as a function of temperature, AG c. = (G°cs.l 0,5) and = (G° - G°, 5) respectively, are... 

The half-period for decrease of muscle cesium-137 concentration in NTS animals after the cessation of atmospheric nuclear weapons testing in 1959 appears anomalous (Table I and Figure 2). In addition to being considerably greater (2.3 years) than the other half-periods found, its standard deviation was larger than the value. If one considers only the initial rate of decrease of radiocesium in these muscle samples, one finds a half-period of 0.9 year which is quite consistent with other data. Examination of these data, in comparison with data from liver (Figures 2 and 3), indicates that only muscle decreased its rate of decline in 1960. It should also be noted that the values during 1960 were only about twice the standard error of analysis. Thus, analytical error alone is not an improbable cause of these anomalous values. 

The chemical yield of each element was usually about 70%. The rubidium content of the 12 County Durham coals was 6-30 ppm, and the cesium content in 10 of the coals was 0.8-3.7 ppm. Reproducibility of results was very good for cesium the relative standard deviation of the mean result was usually less than 5%. Rubidium results were slightly less reproducible, the largest relative standard deviation being 22%. 

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