570 



TABLE 614.— KRYPTON SECONDARY STANDARD WAVELENGTHS 



IN ANGSTROMS 



4273.9700 

 4282.9683 

 4286.4873 

 4300.4877 

 4318.5525 



4319.5797 

 4351.3607 

 4362.6423 

 4376.1220 

 4399.9670 



4453.9179 

 4463.6902 

 4502.3547 

 5562.2257 

 5570.2895 



5649.5629 



5870.9158 



5993.8503 



6421.029 



6456.291 



Neon and krypton secondary standards are used extensively for interference measure- 

 ments in metrology and spectroscopy, but their spectral range and distribution does not 

 make them generally suitable for wavelength measurements by interpolation in prismatic 

 or in grating spectra. For the latter purpose a system of secondary standards should con- 

 sist of lines of comparable intensity distributed as uniformly as possible throughout the 

 entire range of wavelengths commonly observed in optical spectra. An approach to such 

 a system is found in the internationally adopted secondary standards derived from the 

 spectrum of the iron arc. The source for iron secondary standards is specified 185 as the 

 "Pfund arc operated between 110 and 250 volts, with 5 amperes or less, at a length of 

 12-15 millimeters used over a central zone at right angles to the axis of the arc, not to 

 exceed 1.0-1.5 millimeters in width, and with an iron rod 6-7 millimeters diameter as the 

 upper pole and a bead of oxide of iron as the lower pole. As the secondary standards to the 

 red of 6000 A are all stable lines, and as the exposures with the above-mentioned arc 

 may be rather long, it is recommended that the 6 mm, 6 ampere arc be retained for this 

 region." 



The list of iron secondary standards adopted by the International Astronomical Union "* 

 consists of 306 7-figure values ranging from 2447.708 to 6677.933 A, thus covering a little 

 more than one octave. 



Internal evidence from the combination principle as well as the agreement between inde- 

 pendent observers indicates that the average probable error in these standards is ±0.001. A. 

 Preliminary values of long-wave iron lines (6750.158 to 10216.351 A) have been 

 suggested. 187 



Additional ultraviolet iron lines (2100.794 to 3383.980 A) have been suggested 188 and 

 only one or two confirmatory observations are required to extend the secondary standards 

 over a range of more than two octaves. 



186-188 For references, see p. 578. 



TABLE 615.— J VALUES FOR LEVELS IN TERMS HAVING ODD AND EVEN 



MULTIPLICITIES 



TABLE 616.— TERMS FROM NONEQUIVALENT ELECTRONS 



Electrons 

 SP 



sd 



PP 



pd 

 dd 

 df 

 ff 

 etc. 



Terms (omitting / values) 



l S,*S 



ipsp 



l D,*D 



X S, l P, 7?, *S, a P, a D 



1 P, 1 D, 1 F, a P, a D, a F 



\S\ 1 P, 1 D, J F, 1 G, a S, a P, a D, a F, a G 



1 P, l D, *F, 1 G, 1 H, a P, a D, a F, a G, a H 



\S", 1 P, 1 D, 1 F, 1 G, 1 H, 7, a S, a P, a D, a F, a G, a H, 7 



SMITHSONIAN PHYSICAL TABLES 



