Sodium atoms experiments

IV. CROSSED-BEAM EXPERIMENTS WITH LASER-EXCITED SODIUM ATOMS... 

IV. Crossed-Beam Experiments with Laser-Excited Sodium Atoms 359... 

A crucial part of these experiments is the preparation of the sodium atoms into the excited state by laser optical pumping. A commercial single-mode Rhodamin 6G continuous wave (cw)-dye laser (Spectra Physics model 580) is used, having 20-40-mW single mode output power when tuned to the sodium resonance line. 

NaCl The bond in solid sodium chloride is a largely ionic one between Na+ and Cl-. In spite of what we ve said previously, though, experiments show that the NaCl bond is only about 80% ionic and that the electron transferred from Na to Cl still spends some of its time near sodium. A particularly useful way of visualizing this electron transfer is to represent the compound using what is called an electrostatic potential map, which uses color to portray the calculated electron distribution in the molecule. The electron-poor sodium atom is blue, while the electron-rich chlorine is red. 

Flame temperature measurements by the sodium line reversal method were made with hydrazine perchlorate strands containing 2% thiourea and 2% sodium chloride. This amount of sodium chloride was necessary to achieve a sufficient intensity of emission of the sodium D-line for these experiments. It may be pointed out that in oxygen-rich, chlorine-containing flames such as this, the concentration of sodium atoms is decreased... 

Our initial experiments to prepare the radical by the reaction of sodium atoms with phenyl iodide were inconclusive because the resolution was very poor when the parent halide was used as the matrix. Attempts to increase the resolution by using camphane or adamantane as a matrix were unsuccessful as immediately after formation the phenyl radical abstracted hydrogen from the matrix to form benzene and a radical from the matrix. Complete reaction also occurred with matrices of other saturated hydrocarbons which possessed only secondary hydrogens... 

Neff estimated that up to 10% of charge transfer sodium atoms are produced in the excited state, which is consistent with the measurements of Ogurtsov et al. The experiment was not sensitive enough to measuring the corresponding emission cross sections for K+ -t- N2, where the optical transitions are at 770 and 766 nm, respectively. The cross section for exciting the K 5p( Pj) - transitions at 405 nm was found to be... 

The sharp increase in the hidden-Ni concentration on heat treatment was unexpected. We now understand that two processes concur during the reduction of Niii (5 %)Y reduction of hidden NP ions, and reaction between surface sodium ions and sodium atoms to form the Na complexes. This is reasonable because with as low as 5 % cation exchange most of the zeolite cavities are still filled with sodium ions capable of forming the Na complex. This assumption is confirmed by recent experiments in which Ni (5 %)Y on reduction first turned pale red and showed the characteristic spectra of the Na + centres. The paramagnetic electron of the Nal centre so formed evidently then transfers at high temperatures to hidden Ni by the reaction Na -bNin(Si)->4Na+-f Nii(Si), which results in a 5-to 10-fold increase in the concentration of hidden Nil. 

I find myself now at the age of 66 engaged with great excitement in some novel experiments in which we are trying to look at transition states for sodium-atom reactions. It is this project that brings me eerily close to my father s interests of 1929 and subsequent years. 

In a Franck-Hertz experiment on sodium atoms, the first excitation threshold occurs at 2.103 eV. Calculate the wavelength of emitted light expected just above this threshold. (Note Sodium vapor lamps used in street lighting emit spectral lines with wavelengths 5891.8 and 5889.9 A.)... 

Problem 42 in Chapter 9 described an optical atomic trap. In one experiment, a gas of 500 sodium atoms is confined in a volume of 1000 pm. The temperature of the system is 0.00024 K. Compute the probability that, by chance, these 500 slowly moving sodium atoms will all congregate in the left half of the available volume. Express your answer in scientific notation. 

Thakkar and Lupinetti5 have used the coupled-cluster method in conjunction with the Douglas-Kroll relativistic Hamiltonian to obtain a very accurate value for the static dipole polarizability of the sodium atom. Their revised value for a(Na) = 162.88 0.6 au resolves a previous discrepancy between theory and experiment and when combined with an essentially exact value for lithium, establishes the ratio a(Li)/a(Na) = 1.0071 0.0037, so that, because of the... 

The iron vapor-toluene reaction has evoked interest because of the lability of the proposed bis(arene)iron complex to ligand subsitu-tion and to loss of both toluene molecules to free the metal atom. In the latter case the toluene molecules may be usefully regarded as metal atom carriers which can be used to direct the latent reactivity of the atom in subsequent solution phase chemistry. In this way the metal atom experiment can benefit from the convenience and additional versatility afforded by bench-top chemical manipulations. These results are relevant to a reported preparation of a dehydroxy-lated silica-supported Fischer-Tropsch catalyst from a static reactor codeposition of Fe and toluene.(46) In the liquid phase, iron atoms "bottled" in this way have also been utilized in an exceedingly mild method for making minute catalytically active superparamagnetic clusters on the surface and within the cavities of a dehydrated sodium zeolite Y.(38) Using the rotary reactor, preformed solutions of solvated iron atoms (as the toluene complex) are cannulated below their decomposition temperature out of the flask to a cold slurry of the support in toluene. Diffusion of intact... 

Experiments on the emission spectra of hydrogen and sodium atoms indicated that lines in the emission spectra could be split by the application of an external magnetic field. The only way physicists could explain these results was to assume that electrons act like tiny magnets. If electrons are thought of as spinning on their own axes, as Earth... 

It will be noted from Table 13 that single temperature rate coefficients are listed and not Arrhenius parameters. The latter are not readily derived from the original type of experiments, which are not suitable for the measurement of temperature coefficients because of the difficulty of assessing the variations of quantities such as the diffusion coefficient and the limit of detectability of sodium atoms. An interesting competitive method has been developed to study Na and K atom reactions which overcomes these difficulties [146]. The alkali metal atoms were reacted in diffusion flame experiments with pairs of organic halides. By labelling one of the halides with Cl and by analysing for the total concentration and... 

An alternative approach to trace analyte detection results from the measurement of chemiluminescence in a laser-generated plume of plasma, formed when the laser beam evaporates a small amount of sample (43). In these experiments, a pulsed excimer laser-induced-plasma, formed by laser vaporization and ionization, is probed direcdy to measure ion intensity. Ground state sodium atoms, excited state copper atoms, and sodium dimer molecules have all been monitored using this technique. This laser enhanced ionization may well be one of a very few techniques which can be used to probe extremely dense plasmas with good spatial and temporal resolution. 

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