Neon Measurements Research Articles

Vapour pressures of neon of different isotopic compositions

Summary A cryostat was constructed in which it was possible to liquefy neon with the aid of liquid hydrogen. A special apparatus for differential measurements of vapour pressures was made securing a very good heat contact between the bath and the vapour pressure reservoirs. In a bath of liquid or solid neon measurements were carried out about the difference in vapour pressure of neon of different isotopic composition in the atomic weight range between 20.04 and 21.16. It appeared from our measurements that at a fixed temperature the pressure is a linear function of the atomic weight. We derived from our measurements the value of log ϱ20/ϱ22 as a function of temperature. For the solid state a theoretical formula for this quantity is derived and the deviation from this formula, which was found, is discussed. We discussed also the difference in some caloric properties of the two isotopes and derive that the triple point temperature of Ne22 is 0.134 degree above that of Ne20.

Intensity Summation Rules and Perturbation Effects in Complex Spectra

After reviewing the present status of the problem of line intensities in complex spectra, and commenting on the relationship of the sum rule, the extended sum rule, and the general sum rule, a new $J$-group sum rule is derived. A $J$-group is defined as the totality of lines arising from transitions between all terms from one electron configuration having a given value ${J}_{1}$ of the inner quantum number and all terms from a second having a given value ${J}_{2}$; it maintains its identity for all couplings. It is proved that the total intensity of the lines in a $J$-group is independent of coupling, provided a third configuration does not produce terms which perturb those considered; where such perturbation occurs an extension of the new sum rule to an enlarged $J$-group is required. One can accordingly calculate the intensities of the individual lines for $\mathrm{LS}$ coupling, and the total intensities found for each $J$-group or enlarged $J$-group should apply to $\mathrm{jj}$ and all intermediate couplings. Verification of the rule is found in special cases which have been calculated theoretically, and, after ${\ensuremath{\nu}}^{4}$ and excitation corrections have been applied, in Dorgelo's measurements in neon. Where only certain terms of a $J$-group perturb one another lines arising from the remaining terms need not be considered in taking the sums; experimental verification of this is given by measurements in the spectrum of Ti I. Bartlett's statement that the extensions of the sum rule must be modified when configurations containing equivalent electrons are involved is discussed, and a procedure for applying them and the $J$-group sum rule in such cases is suggested. Finally, intensity data for a number of cases in Ti I are given to illustrate the method used in assigning the causes of intensity anomalies in lines to their originating terms, and qualitative results on relationships between term separations and intensity perturbations are given.