Barium line spectrum

After the Curies, with the assistance of M. G. Bemont, had carried out many laborious fractionations of barium chloride, they found that the most insoluble fractions were the most radioactive. In the course of her experiments Mme. Curie had learned that radioactivity is an atomic property depending solely on the quantity of active element present." For this reason the presence of another active element was suspected, and the radioactive barium chloride was therefore submitted to M. Demarcay for spectroscopic examination. He detected a new line in the ultraviolet region of the spectrum, and certain other lines, all of which were most distinct in the most radioactive preparations, and, as fractionation proceeded, the barium lines became fainter and fainter (23, 28, 52). 

Bamford and Ward (1961) have obtained evidence which supports this conclusion, although the systems studied are somewhat different. They used an electric discharge to produce radicals in methacrylic acid (monomer) crystals and in various salts of this acid at 77°K. In some cases relatively narrow lines were obtained, and generally the characteristic nine-line spectrum was observed. Perhaps their most striking result was for the barium salt. At 77°K the four lines were weak and broad, whilst at room temperature a nine-line spectrum of intensity ratio very close to 1 2 4 6 6 6 4 2 1 resulted. These changes were reversed on cooling. 

In 1901 Demarcay made an elaborate series of fractionations of samarium magnesium nitrate which resulted in the discovery of a new earth, europia (3, 31, 59). Since he could read a complex spectrum like an open book, he was frequently called upon to pass judgment on supposedly new elements, and was the first to observe the new lines of radium in some barium salts brought by Pierre Curie. 

The total spectrum should then appear as nine lines of equal width and relative intensities 1 2 4 6 6 6 4 2 1. It is noteworthy that lines 1, 3, 5, 7, and 9 have the correct intensity ratios for the so-called five-line set, and lines 2, 4, 6, and 8 are in accord with experiment for the four-line set. All that is wrong is that the intensity of the four-line set relative to the five-line set is too great except for the barium salt of methacrylic acid at room temperature (Bamford and Ward, 1961). However, the predicted intensities are approached when the spectrum is measured at high temperature, and the deviation at lower temperature arises because of the greater width of the even lines relative to the odd ones. 

The barium light uses the BaO spectrum and the sodium lights, I and II, use the strong spectrum spreading on both sides of the NaD lines. The burning data are shown as a summarized standard in the case of flares loaded at a high pressure. The barium light produces a white flame. 

Fig. 8.16. Experimental spectrum of doubly-excited resonances in the barium spectrum obtained by three-photon spectroscopy. The horizontal arrows in the figure indicate lines which are not spectral features but frequency markers. Because of the mode of excitation, the lines tend to be more symmetrical than in some of the other spectra, but nevertheless exhibit a clear q reversal as the main feature is traversed. A theoretical fit by MQDT is also shown (after F. Gounand et al. [421]).

Why is the OaOl 1 spectrum in Figure 8-8 so much broader than the barium emission line ... 

In most laser studies of optical isotope shifts the crossed, laser-atomic beam method is used to avoid Doppler-broadening. In some cases short-lived radioactive isotopes are detected directly on-line, in others, by irradiating a target which is subsequently heated to form the source of an atomic beam. Figure 7 shows a spectrum obtained some years ago in Oxford on the resonance line of barium at 554 nm S] ... 

The new element was named radium from the Latin radius meaning ray. The birthday of radium was December 26,1898. when the members of the Paris Academy of Sciences heard a report entitled On a new highly radioactive substance contained in pitchblende . The authors reported that they had managed to extract from the uranium ore tailings a substance containing a new element whose properties are very similar to those of barium. The amount of radium contained in barium chloride proved to be sufficient for recording its spectrum. This was done by the well-known French spectral analyst E. Demarcay who found a new line in the spectrum of the extracted substance. Thus, two methods—radiometry and spectroscopy—almost simultaneously substantiated the existence of a new radioactive element. 

Figure 7. High-resolution spectrum of barium Rydberg states. The 6snd D2 series can be followed up to 40 GHz (fi = 290) below the ionization limit. Besides the Dj series (strong signals), P states appear as smaller lines. (Taken from Ref. 36.)...

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