Bath gas

The collision partners may be any molecule present in the reaction mixture, i.e., inert bath gas molecules, but also reactant or product species. The activation k and deactivation krate constants in equation (A3.4.125) therefore represent the effective average rate constants. 

Viggiano A A, Arnold S T and Morris R A 1998 Reactions of mass selected cluster ions in a thermal bath gas Int. Rev. Phys. Chem. 17 147-84... 

Although the transition to difhision control is satisfactorily described in such an approach, even for these apparently simple elementary reactions the situation in reality appears to be more complex due to the participation of weakly bonding or repulsive electronic states which may become increasingly coupled as the bath gas density increases. These processes manifest tliemselves in iodine atom and bromine atom recombination in some bath gases at high densities where marked deviations from TronnaF behaviour are observed [3, 4]. In particular, it is found that the transition from Lto is significantly broader than... 

Although ion transmission guides and ion traps both use the same universal physical laws to achieve control over ion behavior, the ways in which the laws are used are different, as are the objectives. The guides do not retain ions to gain control over their velocities and are used simply to transmit both slow and fast ions over a very wide range of gas pressures. Ion traps retain ions over a relatively long period of time so as to adjust their kinetic energies and thereby improve mass resolution. The so-called bath gas is used at carefully controlled pressures. 

Fig. 14.1 (a) Red shift of Cr emission line peaks as a function of Ar bath gas pressure at 3,230 K. The three curves correspond to the three peaks of the triplet centred on 27,820 cm-1, (b) Corrected MBSL spectra (orange) and Cr emission from a hollow cathode lamp at low pressure (blue). Relative red shifts for each peak are indicated [11] (reprinted with permission from Annual Reviews)... 

Figure 6. Rate constant for the recombination of Cr(CO)4 with CO as a function of bath gas (helium) pressure. The various symbols correspond to data obtained...

The emission spectrum consists of a series of weak bands starting at about 220 nm and then growing into a continuum from about 240 to 400 nm, with a maximum at approximately 270 nm as shown in Figure 5. Halstead and Thrush estimated that =65% of the emission occurs from the B2 state, =15% from the 3B3, and =20% from a combination of the A2 and Bi states [24, 28, 29] with a rate constant of 2 X 1CT31 cm6 molec 2 s 1 using argon as the bath gas at 300 K [53], As with the reaction of SO + 03 discussed above, collisional coupling results in a radiative lifetime that is pressure dependent. 

Worked Example 7.11 Hydrogen gas is mixed with a nitrogen bath gas . The overall pressure is p. If the mole fraction of the hydrogen is expressed as 10 per cent, what is its activity ... 

In a mixture of gases, we call the inert gas a base or bath gas. 

Electrospray ionization (ESI) refers to the overall process by which an intense electric field disperses a sample liquid into a bath gas as a fine spray of highly charged droplets. Evaporation of those charged droplets produces gas-phase ions by mechanisms that remain the subject of much argument and debate. The ESI is a complex of independent component processes, the two most important of which are electrospray dispersion, the electrostatic dispersion of sample liquid into charged droplets, and ionization, the transformation of solute species in those droplets to free ions in the gas phase. 

At the higher pressures of other ion-molecule techniques, such as flowing afterglow or pulsed high-pressure mass spectrometry," both of which operate with a bath gas pressure of about 1 torr, collisions of such an excited intermediate with the bath gas occur on a nanosecond to microsecond time-scale, in competition with the unimolecular dissociation rate. For these techniques, ions that are the... 

Let us take the reaction (10) of OH with S02 as an example of a termolecular reaction of atmospheric interest and examine how its pressure dependence is established. It is common in kinetic studies to follow the decay of one reactant in an excess of the second reactant. In the case of reaction (10), the decay of OH is followed in the presence of excess SOz and the third body M, where M is an inert bath gas such as He,... 

In (15), HOCO is the radical adduct of OH + CO, and HOCO is the adduct containing excess internal energy resulting from the energy released by bond formation between OH and CO. As described earlier, M is any molecule or atom that collides with the HOCO, removing some of its excess energy in practice, it is usually an inert bath gas such as He or Ar that is present in great excess over the reactants. 

Fast-flow systems (FFS) consist of a flow tube typically 2- to 5-crn in diameter in which the reactants A and B are mixed in the presence of a large amount of an inert bath gas such as He or Ar. As the mixture travels down the flow tube at relatively high linear flow speeds (typically 1000 cm s l), A and B react. The decay of A along the length of the flow tube, that is, with time, is followed and Eq. (T) applied to obtain the rate constant of interest. 

In this problem we will consider the kinetics of this unimolecular isomerization reaction in a nitrogen bath gas at 1500 K, using several different theoretical treatments. The high-pressure Arrhenius coefficients for this reaction are A00 = 1 x 1014 s-1 and E0 = 45 kcal/mol. 

Use QRRK theory to calculate kstab and kprod at 1000 K as a function of bath-gas concentration [M] over a range 10-13 to 1012 mol/m3. 

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