Lifetime, atomic

Ozone can be generated by a variety of methods, the most common of which involves the dissociation of molecular oxygen electrically (silent discharge) or photochemicaHy (uv). The short-Hved oxygen atoms (lifetime s) react rapidly with oxygen molecules to form ozone. The widely employed technique... 

Finally, this preliminary experiment, where the microwave interaction time is two orders of magnitude shorter than the atomic lifetime, can be reinterpreted as a R Rydberg constant measurement with a 6x10-9... 

The reactions which occur are controlled by the pressure of gas, electric field strength, reaction chamber dimensions and the gas flow rate. The electric field strength determines the amount of energy imparted to the electrons. The gas pressure and tube dimensions affect the degree of ionization, atomic lifetimes, mean free path and gas temperatures. The gas flow will affect the rate that new reaction material can reach the solid surface ( ). 

A more advantageous approach uses a graphite support (a platform, boat, microboat, cup or probe) for both weighing and atomization. The use of inert supports made of ashless paper and cellulose acetate has also been tested [33]. However, inert supports tend to give high blank values also, the residue remaining after atomization can degrade accuracy and reduce the atomizer lifetime. 

Corrosive action on graphite and pyrocoatings, which has a strong effect on the atomizer lifetime. 

The subject of correlated or collective spontaneous emission by a system of a large number of atoms was first proposed by Dicke [1], who introduced the concept of superradiance that the influence on each atomic dipole of the electromagnetic field produced by the other atomic dipoles could, in certain circumstances, cause each atom to decay with an enhanced spontaneous emission rate. The shortening of the atomic lifetime resulting from the interaction between N atoms could involve an enhancement of the intensity of radiation up to N2. 

Rare earth elements In the past years, many improvements have been made in abundance analyses of the REE through measurements of atomic lifetimes and transition probabilities, notably by the Wisconsin group. A recent paper by [63] summarizes the efforts and gives abundances for the REE. Now the REE abundances are among the best-known abundances for the sun. The following lists several papers on REE that appeared since 2003 the new values for Ce, Dy, Tm, Yb, and Lu are from [63],... 

A more direct method for lifetime measurements is the delayed coincidence technique [6] in which the time between an initiation event and the emission of a decay product is measured. A schematic diagram of an apparatus used for the measurement of atomic lifetimes is shown in figure BLIP.5. The slope of the graph of the natural log of the number of decay events as a function of time delay gives the lifetime directly. The... 

In well-designed experiments the mean hot atom lifetime is much shorter than the mean thermal reactive lifetime. The MNR technique thus oflFers good utility for precise equilibrium kinetics studies wdth the radioactive atoms and unstable radicals produced using nuclear recoil methods. Small residual nonthermal reaction yields are invariably observed in recoil experiments, but these have no direct bearing on the validity of the MNR equilibrium hypothesis. 

Because ESCA can directly probe the electronic structures of substances ranging from free atoms to solids, it is useful in a host of related fields such as stereochemistry, geochemistry, crystallography, and atomic and solid-state physics. Among the phenomena lending themselves to study are stereostructures, band structures, paramagnetism, atomic lifetimes, and Auger transitions. 

Average lifetime of an atom = S (individual atomic lifetimes)/(total number of atoms) = 1.443 H. 

From the measured halfwidth AB /2 the product gjTeff of Lande factor g/ of the excited level 2) times its effective lifetime teff can be derived. For atomic states the Lande factor gj is generally known, and the measured value of A i/2 determines the lifetime teff. Measurements of teff (p) as a function of pressure in the sample cell then yield by extrapolation p 0 the radiative lifetime (Sect. 6.3). The Hanle effect therefore offers, like other Doppler-free techniques, an alternative method for the measurement of atomic lifetimes from the width AB /2 of the signal [832]. 

From the beginning of this century experiments using resonance radiation and resonance fluorescence have been largely responsible for our increasing understanding of excited atoms and their interaction with radiation. In the 1920 s the polarization of resonance fluorescence from atoms subjected to external magnetic fields was studied in detail by Hanle and used to measure radiative atomic lifetimes. 

This chapter opens with an account of resonance fluorescence and its depolarization by external magnetic fields, a phenomenon now knovm as the Hanle effect. Experiments of this type in mercury vapour are described and we develop a classical theory to explain the shape of the observed signals. This is followed by a discussion of the applications of this technique to the accurate measurement of atomic lifetimes. For the sake of simplicity the effects of interatomic collisions and of trapping or reabsorption of resonance radiation in these experiments are not considered... 

The atomic lifetimes measured by the resonance fluorescence techniques range from (2 0 0 2) x 10 s for the T -in... 

The relatively simple apparatus, high sensitivity, and the selective nature of the optical excitation used in many resonance fluorescence experiments combine to make this method the most accurate method for measuring atomic lifetimes. In many cases the experimental measurements may be made at densities which are so low that the effect of resonance trapping and collision broadening are completely absent. In these cases the experimental results are usually quoted with errors in the range 3-5 per cent. The method is suitable for precision lifetime measurements and may for this reason allow a set of relative oscillator strengths obtained by the absorption or emission methods to be placed on a reliable absolute basis. 

Comparison with the Zeeman effect in optical spectroscopy. In optical double-resonance experiments the Doppler shift due to the motion of an atom through the r.f. magnetic field is negligible in comparison with the natural width of the excited levels. Substituting into equation (16.21) a typical atomic lifetime of 10" s leads to a line-width for the magnetic resonance signal, at low r.f. power of... 

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