Argon spectrum

D. P. Shelton and G. C. Tabisz. Binary collision induced light scattering by isotropic molecular gases I. Details of the experiment and the argon spectrum. Molec. Phys., 40-.2i5-291 (1980). 

FIGURE 11.12 He-like and Li-like argon spectrum using quartz (loT) crystal. HF power injected P = 400 W. Argon partial pressure pAr = 5 x 10 mbar, total pressure ptot = 5 x 10 mbar. This spectrum has been obtained with an integration time of 2 h. The focal position of this spectrum was in correspondence to the ls2p Pn — Is Sq peak, near channel 310. 

Spectral interferences are observed in every emission source. These interferences are most important in ICPs because emission lines that might be expected to be weak or nonexistent in other sources such as flames, arcs, or sparks, are quite intense. All spectral interferences originate from the inherent argon spectrum, or from line and continuum spectra of atomic and... 

Figure A3.3.1 Rayleigh-Brillouin spectrum from liquid argon, taken from [4],...

It turns out that the CSP approximation dominates the full wavefunction, and is therefore almost exact till t 80 fs. This timescale is already very useful The first Rs 20 fs are sufficient to determine the photoadsorption lineshape and, as turns out, the first 80 fs are sufficient to determine the Resonance Raman spectrum of the system. Simple CSP is almost exact for these properties. As Fig. 3 shows, for later times the accuracy of the CSP decays quickly for t 500 fs in this system, the contribution of the CSP approximation to the full Cl wavefunction is almost negligible. In addition, this wavefunction is dominated not by a few specific terms of the Cl expansion, but by a whole host of configurations. The decay of the CSP approximation was found to be due to hard collisions between the iodine atoms and the surrounding wall of argons. Already the first hard collision brings a major deterioration of the CSP approximation, but also the role of the second collision can be clearly identified. As was mentioned, for t < 80 fs, the CSP... 

Figure 5.17 shows the rotational Raman spectrum of N2 obtained with 476.5 nm radiation from an argon ion laser. From this spectrum a very accurate value for Bq of 1.857 672 0.000 027 cm has been obtained from which a value for the bond length tq of 1.099 985 0.000 010 A results. Such accuracy is typical of high-resolution rotational Raman spectroscopy. 

Figure 8.6 The He I ultraviolet photoelectron spectrum of argon. (Reproduced from Turner, D. W., Baker, C., Baker, A. D. and Brundle, C. R., Molecular Photoelectron Spectroscopy, p. 41, John Wiley, London, 1970)...

IR and Raman studies of heterocycles today cover two different fields. For simple and symmetrical molecules very elaborate experiments (argon matrices, isotopic labelling) and complex calculations lead to the complete assignment of the fundamentals, tones and harmonics. However, the description of modes ought to be only approximate, since in a molecule like pyrazole there are no pure ones. This means that it is not correct to write that the band at 878 cm is y(CH), and the only correct assertion is that the y(CH) mode contributes to the band. On the other hand, IR spectroscopy is used as an analytical tool for identifying structures, and in this case, bands are assigned to r-iCO) or 5(NH) on the basis of a simple Nujol mull spectrum and conventional tables. Both atttitudes, almost antagonistic to each other, are discussed in this section. 

Precise description of the pyramidal structures would also require that the bond angles be specified. The EPR spectrum of the methyl radical leads to the conclusion that its structure could be either planar or a veiy shallow pyramid. The IR spectrum of the methyl radical has been recorded at very low tempertures in frozen argon. This IR study puts a maximum of 5° on the deviation from planarity. A microwave study has also indicated... 

Photolysis of the 1,2,3-trithiole 42 in argon matrix (20 K) gave an electronic spectrum exhibiting the absorption maxima at 455 and 340 nm. Tlie spirodithiirane 43 and the thiosulfoxide 44 were believed to be responsible to these absorptions (89TL2955). 

Excimer lasers use gases, but because of their special properties are usually considered as a class of their own. Excimer is short for excited dimer, which consists of two elements, such as argon and fluorine, that can be chemically combined in an excited state only. These lasers typically emit radiation with veiy small wavelengths, in the ultraviolet region of the electromagnetic spectrum. This shorter wavelength is an enormous advantage for many applications. 

In the continuous wave (CW) experimental setup a sample is constantly illuminated by a probe beam and the steady state change in the transmission is detected (see Fig. 7-1). An argon ion laser has been used to generate the pump beam and the probe beam was from an incandescent lamp (tungsten or others), producing a broad spectrum (0.5 to 5 pm) [6]. Both pump and probe beams are directed onto the sample film and the transmitted probe light is collected, filtered through a monochromator, and detected by a photodetector. Both the pump and the probe... 

Four IR absorption bands have been identified in the spectrum of the hydroxysulfonyl radical (HOSO 2) which has been obtained by the reaction of hydroxyl radicals with sulfur dioxide in argon matrix at 11 K16. The observed bands at 3539.9 and 759.5 cm 1 have been assigned to O—H and S—OH stretching modes while the bands at 1309.2 and 1097.3 cm-1 have been assigned to the asymmetric and symmetric stretching modes of the double bonded S02 moiety. These data are consistent with the theoretical prediction on the geometry of the hydroxysulfonyl radical12. 

Fig. 2.4. The asymptotic behaviour of the IR spectrum beyond the edge of the absorption branch for CO2 dissolved in different gases (o) xenon (O) argon ( ) nitrogen ( ) neon (V) helium. The points are experimental data, the curves were calculated in [105] according to the quantum J-diffusion model and two vertical broken lines determine the region in which Eq. (2.58) is valid.

Fig. 6.4. The recovery of the gap in the IR spectrum of CO in argon [266]. The numbers denote the density of argon in amagat.

Fig. 12. Mossbauer spectrum of an argon matrix containing iron and nickel (59).

Species such as 5 and 6 are called benzynes (sometimes dehydrobenzenes), or more generally, arynes, and the mechanism is known as the benzyne mechanism. Benzynes are very reactive. Neither benzyne nor any other aryne has yet been isolated under ordinary conditions, but benzyne has been isolated in an argon matrix at 8 where its IR spectrum could be observed. In addition, benzynes can be trapped for example, they undergo the Diels-Alder reaction (see 15-58). It should be noted that the extra pair of electrons does not affect the aromaticity. The... 

Raman spectra of S2 in its triplet ground state have been recorded both in sulfur vapor and after matrix isolation using various noble gases. The stretching mode was observed at 715 cm in the gas phase [46], and at 716 cm in an argon matrix [71]. From UV absorption and fluorescence spectra of sulfur vapor the harmonic fundamental mode of the S2 ground state was derived as t e = 726 cm . The value corrected for anharmonicity is 720 cm [26, 27]. Earlier reports on the infrared absorption spectrum of 2 in matrix isolated sulfur vapor [72] are in error the observed bands at 660, 668 and 680 cm are due to S4 [17] and other species [73]. 

---