Gases early experiments

By the late 1940s methods of ionization counting had been developed for the estimation of 14C. Thin layers of suitably prepared material could be counted in windowless counters, with the emissions being detected by the probe in a flow of inert gas. Otherwise 14C-containing material could be combusted to 14C02 and this drawn over the probe. Neither method was very convenient to use and the instruments were costly. Early experiments with 14C were mainly performed in the U.S. (see below). 

The well-known catalytic additive to MgH is Ni. So far, it has been added as a coarse powder with the size range of a few tens of micrometers. A short review of these early experiments is presented in [117], More recently, Hanada et al. [118] investigated the addition of nano-Ni to ball-milled MgH. Unfortunately, he used continuous desorption under He gas and the material desorbed 6 wt.%H2 at 160°C in 15,000 s. 

In the early experiments, when gas-solid adsorption was studied by some 200 years ago, charcoal was the most widely used adsorbent [12]. These investigations, generally limited to adsorption from dilute solutions, gave adsorption isotherms of the form shown in Figure 10.4. These isotherms could be fitted by the equation ... 

Chemical techniques of analysis deal with a very large number of atoms and yield averages over the sample. Once the concept of isotopes was accepted, a search for different isotopes of every element was pursued. The key to the success of this search was the development of a precision instrument that sampled the atoms one at a time. It had been known since the development of the cathode ray tube that positive ions were also produced, and early experiments with these particles revealed singly and doubly charged species of the atoms and molectrles that were contained in the tube. Sir J.J. Thomson observed in 1912 that when neon was the background gas, particles of mass ntrmber 20 and 22 were observed. Attempts to obtain pure samples of the two different atoms by fractionation techniques were unsuccessful, but in retrospect this was because they were both neon isotopes. 

The activated dissociation of H2 (D2) on Cu(l 11) and other single crystal Cu surfaces has played a special role in the development of reactive gas-surface dynamics. Early experiments and theory by Cardillo and collaborators [217-219] first demonstrated the power of molecular beam techniques to probe activated adsorption and the theoretical methodology developed by them (6D quasi-classical dynamics on a model PES) only differs from modem treatments in the use of DFT based PES. 

Figure 21. Emission in the 1800-2800 cm-1 region following the IRMPD of CH2F2 (25 mTorr) in the presence of NO (lOOmTorr) and Ar (lOTorr). Emission from N20 (001) and C02 (001) are seen at long times following the vibrational cascade of highly excited species their presence at early times [together with CO(v = 1)] was established by cold gas filter experiments. N20 is the dominant emitter, and is believed to originate from the reaction sequence (20), (17).

The results of early experiments showed that the temperature did not change on the expansion of the gas, and consequently the value of the Joule coefficient was zero. The heat capacity of the gas is finite and nonzero. Therefore, it was concluded that (dE/dV)Tn was zero. Later and more-precise experiments have shown that the Joule coefficient is not zero for real gases, and therefore (dE/dV)Ttheoretical concepts of the ideal gas. 

Therefore, it would be advantageous to perform the chemical synthesis of the volatile molecule in-situ in the recoil chamber. This approach has already been used in the very first chemical studies of transactinides, see Section 4.3. Chlorinating and brominating agents were added to a carrier gas in order to form volatile halides of the 6d elements. However, in these early experiments only tracks of SF events were revealed after completion of the experiment. Obviously, such a technique has the disadvantage of not... 

Other experiments were carried out also on the decomposition of carbon dioxide, the decomposition of hydrochloric acid gas and the oxidation of alcohol vapor. In no case was chemical action brought about by the absorption of an intense beam of infrared radiation. Furthermore, no case of chemical reactivity produced by longer infrared radiation has been established in the literature. Increases in reaction rates in early experiments can be traced to an increase in the temperature of the solution produced by the absorption of the heat rays. A few cases of activity of short infrared rays of 1 jx and less are on record in special reactions. 

The effects of liquid velocity (at least at low velocities), direction of flow and liquid properties are only minor for Newtonian fluids. Correlations on gas-liquid columns are given by Joshi [63], Field and Davidson [64] measured the dispersion in a large industrial column (de - 3.2 m, H — 19 m) and found agreement with the correlations of Dcckwer et al. [65] and Joshi [63] (Tabic 3). The influence of particles can be expected to be small, at least for low concentrations and small particles. This is confirmed by the early experiments of Kato et al. [15, 69], For particle sizes ranging from 63... 

Early experiments were concerned with the protection against water-vapor adsorption afforded a pair of soft steel electrodes by coating each with FEP Teflon resin. The two coated electrodes were cleaned as before, mounted in the gas cell, and then discharged with gaseous ions while the metal pins were grounded. The resulting contact potential difference was zero. The same result was obtained using a pair of resin-coated aluminum electrodes. 

The concept of the Raman echo extends back to Hartmann in 1968 (27), and a few early experiments were performed on gas-phase electronic (28,29) and vibrational (30) transitions. However, it was the paper by Loring and Mukamel in 1985 that pointed out the importance of the Raman echo for studying condensed-phase vibrational dephasing (26). Initial attempts to perform the Raman echo in liquids failed (31), but technical improvements allowed the first successful Raman echo experiment in a liquid in 1991 (3). 

Despite the fact that a transition metal-noble gas complex has been isolated only very recently, the study of nohle gas coordination of transition metals actually has a long history. Early experiments used the technique of matrix isolation 18). Under the cryogenic conditions of frozen inert matrices, highly reactive photoproducts become sufficiently long-lived to allow their detection at leisure by conventional spectroscopic techniques such as UV/visible, IR, and EPR spectroscopy. 

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