Excited xenon atoms

The quenching of Xe(6s, 3p ) metastable atoms by phosgene has been studied [1146,1844], and the vibrational energy transfer monitored [2004]. The reaction of excited xenon atoms (3 or 3p ) th phosgene generates XeCl(B,C), the emission from which, XeCl(B-.X ) and XeCl(C-A), has enabled vibrational relaxation and transfer between the B and C states to be studied in some detail [263,558]. 

As for XeF the X-ray component for irradiated Xe/CH2Br2 was negligibly small. The xenon dimer fluorescence was typically complete within 100 ns and its intensity was proportional to the xenon pressure. The exciplex fluorescence formed by the reaction of excited xenon atoms with CH2Br2 was also observed within the first hundred nanoseconds, however its intensity was strongest at low xenon pressures. The ionic recombination formed exciplex fluorescence again had the slowest rate of production, being observed for many hundreds of nanoseconds. Its intensity was also dependent on total xenon gas pressure being comparable to the excited-state formed fluorescence at low... 

For XeBr formation, the greater C-Br bond strength of 3.06 eV [93] and the higher second energy level for the excited state of Br of 8.31 eV [94] would mean that only the upper 2p levels of the excited xenon atoms would be able to produce this electronically excited halide atom. Since the population of these high excited states is lower, the amoimt of reaction proceeding by this pathway would be less, giving a concomitant increase in the yield of exciplex production, as observed. 

The compound of interest is dissolved in a high-boiling viscous solvent such as glycerol a drop is placed on a thin metal sheet, and the compound is ionized by the high-energy beam of xenon atoms (Xe). Ionization by translational energy minimizes the amount of vibrational excitation, and this results in less destruction of the ionized molecules. The polar solvent promotes ionization and allows diffusion of fresh sample to the surface. Thus ions are produced over a period of 20-30 min, in contrast to a few seconds for ions produced from solid samples. 

In the Xe-BrCCl3 complex, excitation of the complex at 247 nm leads exclusively to the XeBr(B, C) formation. The fixed geometry of the complex can explain this result. If, in the complex, the xenon atom is directly bonded to the bromine atom, then the proximity of these two atoms can induce this selectivity. 

In this review of the high pressure sodium lamp, emphasis is placed on evidence concerning the interaction of resonantly excited sodium atoms with sodium, mercury or xenon atoms, which modifies the spectral radiance of lamps to improve the color or efficacy. The influence of mercury and xenon buffer gases on tne thermal and electrical conductivities and hence on lamp efficacy are also indicated. 

This procedure provides a model of the xenon atom which accounts only for the manifold of singly excited states based on the lowest ionic core, P3/2- For all rare gases, a second manifold of states converges to the next spin-orbit component of the ion, the Pi/2 state. For example, these two ionization limits in xenon are separated by 1.3 eV corresponding to different total angular momenta, J, of the 5p configuration. The lower ionization potential is 12.15 eV. We assume that multiphoton excitations into these two manifolds are very weakly coupled so they can be treated separately. This assumption is reasonable because once one of the electrons is excited outside a particular core configuration, transitions... 

Kelley and Rentzepis [297] have recently studied the recombination of iodine atoms in liquid and fluid xenon over times to 150 ps after photolysis. The iodine molecule can be biphotonically dissociated through the state to produce geminate pairs with larger initial separations. Some degree of spin relaxation of excited iodine atoms ( Pi/2) produced by biphotonic excitation may occur and reduce the probability of recombination. There is also evidence that the 11 state of I2 may be collisionally predissociated and that recombination may be more rapid than the rate of vibrational relaxation of the excited 12 state in polyatomic solvents (see also ref. 57). Despite these complications, several workers have attempted to model the time dependence of the recombination (or survival) probability of iodine atom reactions. The simple diffusion equation analysis of recombination probabilities [eqn. 

The bottom-up approach involves making nanostructures and devices by arranging atom by atom. The scanning tunnelUng microscope (STM) has been used to build nano-sized atomic features such as the letters IBM written using xenon atoms on nickel 5 (Figure 1.6). While this is beautiful and exciting, it remains that the... 

Moleculair dynamics calculations have been carried out (Bado et al. 1982) from trajectory simulations of two iodine atoms surrounded by fifty xenon atoms these authors were able to take account of solvent caging, atomic recombination and vibrational relaxation to the solvent. Tramsient electronic absorption spectra of iodine were calculated during the first 800 ps following laser excitation. From these spectra, transient kinetics at any wavelength cam be obtained. 

Calculate the difference in energy between the ground state and the first excited translational level of a xenon atom in a box 0.100 m on each side. Express it in joules and in electron volts. Compare it with the corresponding value for a hydrogen atom in Example 22.1, and also compare it with the excitation energy to the first excited electronic level of the xenon atom, 8.315 eV. 

Find the values of the three translational quantum numbers (assumed equal) of a xenon atom in a cubical box 0.200 m on a side if the translational energy is equal to 8.315 eV, the excitation energy to the first excited electronic... 

Despite its simplicity, the model was applied with great success to, e.g., the STM-driven transfer of a xenon atom on a nickel surface. This pioneering experiment was the very first example of an STM-controlled atomic switch, where the xenon atom was moved from the nickel surface to the tungsten STM tip. Figure 6 shows the comparison between theoretical and experimental transfer rates for different values of the ratio The computed transfer rates are inferred from an implicit dynamics between truncated harmonic oscillators, with the initial conditions chosen as the fifth excited vibrational state located on the surface. This corresponds to a situation where above-threshold dynamics dominates. By construction, the rates exhibit the proper power-law dependence with increasing potential bias. It is found that, for this... 

In AFS, the analyte is introduced into an atomiser (flame, plasma, glow discharge, furnace) and excited by monochromatic radiation emitted by a primary source. The latter can be a continuous source (xenon lamp) or a line source (HCL, EDL, or tuned laser). Subsequently, the fluorescence radiation is measured. In the past, AFS has been used for elemental analysis. It has better sensitivity than many atomic absorption techniques, and offers a substantially longer linear range. However, despite these advantages, it has not gained the widespread usage of atomic absorption or emission techniques. The problem in AFS has been to obtain a... 

Matrix Isolation Spectroscopy. Gaseous hydrazoic acid and xenon (1/200) were condensed on a Csl disk cooled to 28-35 K. Exposure of the mixture to 254-nm radiation led to the consumption of HN3 and the formation of new vibrational bands at 3131.8, 3120.6, and 3109.0 cm assigned to triplet NH. The use of xenon as the matrix host is crucial to the success of the experiment. The heavy atom host accelerated intersystem crossing in either the excited state of HN3 or NH, which led to good yields of... 

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