Cesium optical

Rubidium was discovered ia 1861 by Bunsen and Kirchoff by means of an optical spectroscope. It was named for the prominent red lines ia its spectmm, from the Latin word rubidus meaning darkest red. Bunsen prepared free mbidium duriag the same year by an electrolytic method. After cesium, mbidium is the second most electropositive and alkaline element. The two isotopes of natural mbidium are Rb [13982-12-1] (72.15%) and Rb [13982-13-3] (27.85%). The latter is a beta-emitter having a half-life of 4.9 x 10 ° yr. Twenty-four isotopes of mbidium are known. 

Other. Alkali chiorochromate compounds, including cesium chiorochromate, CsCrCl, are ferromagnetic substances being studied for potential apphcation in optically-read computer memory devices. Cesium has also been used in vapor glow lamps (44), vapor rectifiers, and high energy lasers (qv)... 

Other Applications. The refractive index of siUcate or borosiUcate glass can be modified by the addition of cesium oxide, introduced as cesium nitrate or carbonate. Glass surfaces can be made resistant to corrosion or breakage by surface ion exchange with cesium compound melts or solutions. This process can also be used for the production of optical wave guides (61). 

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. 

D-a-Hydroxy carboxylic acids.1 These optically active acids can be prepared by a Sn2 reaction between the t-butyl esters of L-2-halo carboxylic acids and cesium p-nitrobenzoate, which proceeds with complete inversion. 

Cesium is used in military infrared devices and signal lamps as well as in other optical devices. 

Many elements are present in the earth s crust in such minute amounts that they could never have been discovered by ordinary methods of mineral analysis. In 1859, however, Kirchhoff and Bunsen invented the spectroscope, an optical instrument consisting of a collimator, or metal tube fitted at one end with a lens and closed at the other except for a slit, at the focus of the lens, to admit light from the incandescent substance to be examined, a turntable containing a prism mounted to receive and separate the parallel rays from the lens and a telescope to observe the spectrum produced by the prism. With this instrument they soon discovered two new metals, cesium and rubidium, which they classified with sodium and potassium, which had been previously discovered by Davy, and lithium, which was added to the list of elements by Arfwedson. The spectroscopic discovery of thallium by Sir William Crookes and its prompt confirmation by C.-A. Lamy soon followed. In 1863 F. Reich and H. T. Richter of the Freiberg School of Mines discovered a very rare element in zmc blende, and named it indium because of its brilliant line in the indigo region of the spectrum. 

Fig. 3. Eloetron-optical reproduction of a crystalline nickel plate emitting thermionic electrons in cesium vapor [according to Schenk (31)].

Optical wave guides -boron trichloride m prodn of pORON COMPOUNDS - BORON HALIDES] (Vol 4) -cesium m [CESIUM AND CESIUM COMPOUNDS] (Vol 5) -vitreous silica in [SILICA - INTRODUCTION] (Vol21)... 

Photomultipliers -cesium in [CESIUMAND CESIUM COMPOUNDS] (Vol5) -m infrared technology [INFRARED TECHNOLOGY AND RAMAN SPECTROSCOPY - INFRARED TECHNOLOGY] (Vol 14) -for optical spectroscopy [SPECTROSCOPY, OPTICAL] (Vol 22) -silicon carbide m [CARBIDES - SILICON CARBIDE] (Vol 4) -use m kinetic measurements [KINETIC MEASUREMENTS] (Vol 14) -usem optical spectroscopy [SPECTROSCOPY, OPTICAL] (Vol 22)... 

In 1991. a research team tEcole Normal Superieure. Parist reported the cooling of a sample of cesium atoms to 2.5 pK. At about the same lime, a research group (.hunt Institute for Laboratory Astrophysics. Boulder. Coloiado) inputted the achievement ol 5 iK The aforementioned "optical molasses" technique was used in both eases. 

Rate studies of the reaction between cesium and water in ethylenediamine, using the stopped-flow technique, have been extended to all alkali metals. The earlier rate constant (k — 20 NT1 sec.-1) and, in some cases, a slower second-order process (k — 7 Af"1 sec.-1) have been observed. This is consistent with optical absorption data and agrees with recent results obtained in aqueous pulsed-radiolysis systems. Preliminary studies of the reaction rate of the solvated electron in ethylenediamine with other electron acceptors have been made. The rate constant for the reaction with ethylene-diammonium ions is about 105 NCl sec.-1 Reactions with methanol and with ethanol show rates similar to those with water. In addition, however, the presence of a strongly absorbing intermediate is indicated, which warrants more detailed examination. 

Earlier work (6) using this method yielded a second-order rate constant of 24.7 1.5 M""1 sec."1 for the reaction of dilute solutions of cesium with water in ethylenediamine. On the basis of optical absorption spectra (7) and other evidence (8, II), it was assumed that this reaction was that of the solvated electron as well as loosely bound electrostatic aggregates of electrons and cations with water. This permitted correlation with the results of aqueous radiation chemistry. 

The rest of the apparatus is the same as when operated at the Proton Synchrotron. First tested on cesium [ HUB 78 ], [ THI 81 ] the apparatus was used to uncover the resonance lines of francium for which no optical transition had ever been observed. The CERN on line mass separator, Isolde, makes available a source of more than 10 atoms/sec of chemically and isotopically pure 213 Fr isotope. Such an amount is more than needed for a laser atomic beam spectroscopy. The first step is obviously to locate the resonance line at low resolution, using a broad band laser excitation. In a second step, once the line is located, a high resolution study is undertaken, [ LIB 80] and [ BEN 84]. The observed signal is displayed (fig 3a) at low resolution and(3 b)at high resolution. 

Fig. 11. Correlation of optical and ESR data for monomeric forms of potassium and cesium in a variety of host matrices. [From Edwards and Catterall (65) used with permission of Taylor and Francis, Ltd., Philosophical Magazine.]...

Fig. 17. Optical spectra of lithium, sodium, potassium, rubidium, and cesium in ethylenediamine with identification of absorption peaks of Na, K, Rb, Cs and er. Absorption for es is taken from pulse radiolysis studies. [Taken from Fig. 1 of Dye (57) used with permission of Verlag-Chemie, Angew. Chem.Int. Ed. Engl.]...

The existence of these different practices was not sufficient to create a discipline or subdiscipline of physical chemistry, but it showed the way. One definition of physical chemistry is that it is the application of the techniques and theories of physics to the study of chemical reactions, and the study of the interrelations of chemical and physical properties. That would mean that Faraday was a physical chemist when engaged in electrolytic researches. Other chemists devised other essentially physical instruments and applied them to chemical subjects. Robert Bunsen (1811—99) is best known today for the gas burner that bears his name, the Bunsen burner, a standard laboratory instrument. He also devised improved electrical batteries that enabled him to isolate new metals and to add to the list of elements. Bunsen and the physicist Gustav Kirchhoff (1824—87) invented a spectroscope to examine the colors of flames (see Chapter 13). They used it in chemical analysis, to detect minute quantities of elements. With it they discovered the metal cesium by the characteristic two blue lines in its spectrum and rubidium by its two red lines. We have seen how Van t Hoff and Le Bel used optical activity, the rotation of the plane of polarized light (detected by using a polarimeter) to identify optical or stereoisomers. Clearly there was a connection between physical and chemical properties. 

Abstract. A suitable femtosecond (fs) laser system can provide a broad band comb of stable optical frequencies and thus can serve as an rf/optical coherent link. In this way we have performed a direct comparison of the IS — 2S transition in atomic hydrogen at 121 nm with a cesium fountain clock, built at the LPTF/Paris, to reach an accuracy of 1.9 x 10-14. The same comb-line counting technique was exploited to determine and recalibrate several important optical frequency standards. In particular, the improved measurement of the Cesium Di line is necessary for a more precise determination of the fine structure constant. In addition, several of the best-known optical frequency standards have been recalibrated via the fs method. By creating an octave-spanning frequency comb a single-laser frequency chain has been realized and tested. 

To summarize we have presented here a new concept for measuring optical frequencies, based on a well-stabilized train of optical impulses. This new technique has been applied to the measurement of the hydrogen IS — 2S transition, to calibrate iodine stabilized HeNe lasers, and to the Cesium Di line which is a cornerstone for a new determination of a. This development culminates in the fully phase locked single-laser optical frequency synthesizer. It uses a single femtosecond laser and is nevertheless capable of phase coherently linking the rf domain with a whole octave of optical frequencies. It occupies only 1 square meter on our optical table with considerable potential for further miniaturization. 

To compare the theory of ae with experiment, it is necessary to know the value of a, which has been measured in diverse branches of physics. Currently best values of a, with relative standard uncertainty of 1 x 10-7 or less, are those based on the quantum Hall effect [32], the ac Josephson effect [25], the neutron de Broglie wavelength [33], the muonium hyperfine structure [34,35], and an absolute optical frequency measurement of the Cesium >1 line [36] ... 

---