Rare gases, liquid form

The acetates of monosaccharides are sufficiently volatile that they may be used for gas-liquid chromatography, but they are less readily formed than the trimethylsilyl derivatives, and still present the problem of anomeric derivatives (see Section IV, p. 38). They are, therefore, rarely used, but the method is discussed in Section V.2 (see p. 49), and the known cases are presented in Table II (see p. 111). 

The liquid-liquid interface formed between two immissible liquids is an extremely thin mixed-liquid state with about one nanometer thickness, in which the properties such as cohesive energy density, electrical potential, dielectric constant, and viscosity are drastically changing from those of bulk phases. Solute molecules adsorbed at the interface can behave like a 2D gas, liquid, or solid depending on the interfacial pressure, or interfacial concentration. But microscopically, the interfacial molecules exhibit local inhomogeneity. Therefore, various specific chemical phenomena, which are rarely observed in bulk liquid phases, can be observed at liquid-liquid interfaces [1-3]. However, the nature of the liquid-liquid interface and its chemical function are still less understood. These situations are mainly due to the lack of experimental methods required for the determination of the chemical species adsorbed at the interface and for the measurement of chemical reaction rates at the interface [4,5]. Recently, some new methods were invented in our laboratory [6], which brought a breakthrough in the study of interfacial reactions. 

In the period 1940-1946, Ogg (132) developed the first quantitative theory for the solvated electron states in liquid ammonia. The Ogg description relied primarily on the picture of a particle in a box. A spherical cavity of radius R is assumed around the electron, and the ammonia molecules create an effective spherical potential well with an infinitely high repulsive barrier to the electron. It is this latter feature that does not satisfactorily represent the relatively weakly bound states of the excess electron (9,103). However, the idea of a potential cavity formed the basis of subsequent theoretical treatments. Indeed, as Brodsky and Tsarevsky (9) have recently pointed out, the simple approach used by Ogg for the excess electron in ammonia forms the basis of the modem theory (157) of localized excess-electron states in the nonpolar, rare-gas systems. [The similarities between the current treatments of trapped H atoms and excess electrons in the rare-gas solids has also recently been reviewed by Edwards (59).]... 

Many specially designed arc apparatus have been patented for the plasma treatment of petroleum fractions146- 151 Some of these permit cracking gas-liquid mixtures or gas-solid mixtures in continuous process with recycling of undecomposed petroleum. In one such device147 crude oil is mixed with an energy transfer medium (rare gas, alkali metal vapor) and the mixture formed into particles which are fed through the hollow cathode of an electrical arc sustained in the transfer medium. 

The first indications that certain systems might violate the phase rule came from computer simulations of small clusters of atoms. A number of studies revealed clearly defined solid-like and liquid-like forms [5-14]. These embraced both molecular dynamics and Monte Carlo simulations, and explored a variety of clusters. These included several based on atomic models with interparticle Lennard-Jones forces, which mimic rare gas clusters rather well. There were also models of alkali halide clusters. Hence, the existence of solid and liquid forms for such small systems seemed not only plausible but general, not restricted to any one kind of system. Shortly after these studies appeared, another, of a 55-atom cluster with Lennard-Jones interparticle forces, showed not only solid and liquid forms but also a form in which the surface of the cluster (with icosahedral structure) is liquid... 

The first spectroscopic evidence for a M-H2 interaction was obtained by Sweany just prior to our initial neutron diffraction study in 1982 Photolysis of Cr(CO)6 in the presence of H2in a rare-gas matrix was claimed to give ( )5( 2) based on vco.32 However, these results were admittedly difficult to publish until after our seminal paper appeared. At about the same time related papers also showed that Cr(CO)5(H2) could be formed in liquid Xe or cyclohexane but is stable for only seconds at room temperature.33 It is important to note that these findings proved that sterically demanding coligands are unnecessary for H2 coordination per se but can impart thermal stability electronically and/or by stabilizing the 16e precursor by an agostic interaction. 

In geologic conditions nonpolar, hydrophobic substances under consideration, depending on pressure and temperature are capable of changing their phase state and can be gaseous, liquid or even solid. In gas state they form underground gas whose composition is dominated by such components as CH, more rarely and very rarely CO. Liquid nonpolar substances are mobile solutions (crude oil, oil products, residual oil, etc.,) whose composition is dominated by complex non-volatile organic compounds, namely, liquid alkanes (from pentane to heptadecane), almost all naphthenes, numerous aromatic hydrocarbons (benzene, toluene, isopropyl benzene, etc.), which in pure form may have melting temperature below 0 °C. 

When M = oxidative addition occurs, but the alkyl and hydride ligands are readily replaced by [CpRh(CO)], leading to dimerization. Similar investigations have been conducted at reduced temperatures in liquified rare gases.Liquid xenon especially is a good, inert solvent for alkane activation reactions. A weak solvent complex is formed with the rare gas (M—Kr < M—Xe, despite lower temperature for liquid Kr), according to Scheme This is replaced by alkane... 

Bergman and coworkers have applied liquid Xe as a useful solvent for C—H activation. For the Cp IrLH2 system, it allowed study of methane, as well as of more exotic alkanes, such as cubane and adamantane in the latter case the 2-adamantyliridium hydride was formed on irradiation" ". In addition, time-resolved IR spectroscopic studies were carried out in Xe and Kr which led to the proposal that alkane complexes are in equilibrium with rare gas complexes in this system (equation 14). The alkane complex is the last observed precursor before the alkyl hydride is formed". ... 

As described in the Introduction, free-jet spectra of radicals and ions can be produced by the photolysis or photoionization of a stable precursor seeded into a rare-gas expansion. The stable molecule is seeded into the jet by passing the high pressure carrier gas over a liquid or solid sample maintained at a fixed temperature. The percentage mixed into the carrier can be simply varied by changing the temperature of the precursor reservoir and hence the vapor pressure of the sample. The seeded rare gas is then expanded through a pinhole to form a cw expansion as shown schematically in Fig. 2. 

In small channels, a number of flow patterns can be observed, and the same terminology and classifications as in large channels are commonly used. Because of the dominance of the surface tension forces, stratified flow is rarely observed in small channels. In general, bubble flow appears at low gas flow rates. As the gas flow rate increases, Taylor bubbles form. With further increase in the gas flow rate, annular flow appears with the liquid forming an annulus which wets the wall. At high gas and liquid flow rates, chum flow occurs where there is a liquid film at the wall and the gas flow in the center is interrupted by the firequent appearance of frothy bubbles and slugs. 

Laboratories and in 1966 the blue helium-cadmium metal vapor ion laser discovered by W. T. Silfvast, G. R. Fowles, and B. D. Hopkins at the University of Utah. The first liquid laser in the form of a fluorescent dye was discovered that same year by R P. Sorokin and J. R. Lankard of the IBM Research Laboratories, leading to the development of broadly tunable lasers. The first of the rare-gas-halide excimer lasers was first observed in xenon fluoride by J. J. Ewing and C. Brau of the Avco-Everett Research Laboratory in 1975. In 1976, J. M. J. Madey and co-workers at Stanford University developed the first fi ee-electron laser amplifier operating at the infi ared carbon dioxide laser wavelength. In 1985 the first soft X-ray laser was successfully demonstrated in a highly ionized selenium plasma by D. Matthews and a large number of co-workers at the Lawrence Livermore National Laboratory. 

Chlorine is a highly reactive reagent which is now available in large quantities relatively cheaply, although it suffers the disadvantage that it must be transported in liquid form under pressure, contained in stout steel cylinders or drums. An ore breakdown method which has been applied in the rare metal field to titanium, zirconium, hafnium and uranium, is to pass chlorine gas at high temperature over an intimate mixture of the mineral oxide with carbon, A mixture of carbon monoxide and carbon dioxide is... 

---