DR. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 



421 



RITZ Combinations. The results obtained enable us to test for additional series, 

 associated with the name of RITZ who first pointed out their existence. They are 

 represented by the expressions n = P(l)-/(m), and s (l)-f(m). Here p (l) = 8 ( o>) 

 = 51025'30 and/(m) is given by the formula on (p. 412). s(l) = P(oo) = 93178*69 

 and should give a parallel series 42153*39 ahead, and therefore in the extreme ultra- 

 violet. The results are for the sets p,, p 2 , p 3 . 



m. 

 2. 

 3. 

 4. 

 5. 



Calc. pi -f(m) . d\. 

 38665-21 -'07 

 44105'93 '18 

 46607-42 '03 

 47961-81 '06 



(1) 38666-56 1784'06 



(44102-34) 1783-08 



(46606-52) 1784-28 



(47960-42) 1777-90 



Observed. 



(2) 40450-62 806'91 

 (45885-42) 815'66 

 (48390-80) 807-29 

 + 813-68 



(1) 41257-53 

 (46701-08) 

 (49198-09) 



(50552-00) 



Notes. m = 2. 1784*06 + 806*91 = 1777 - 90 + 813'07 



m = 3. There is some ambiguity as to F 3 (3), which gives the calculated value. 

 The deduced ultra-violet lines are from the observed triplet by the e link. 



(7)36788-24 



Also 



1783*08 (2) 38571'32 805'66 (1)39386-98. 

 32362-98 1777'90 (<l) 34140*88 give 44105*08, 45882*98. 



u + (2) 39969-62 = 44102'8 with the i/,, v , lines in the ultra-violet, but an extra 

 v sounder gives u + v + (2) 37320'68 813'93 (l) 38134*6 1 = 45881 '86, 4669579, 

 the former being 1779'06 ahead of'44102'80. 



m = 4. e + (l) 39292*42 1784'28 (1)4107670 = 46606*52, 48390'80 with 

 2e + (4) 34569-89 = 49198'09 which is 1777'90 + 813-67 above 40606. 



m = 5. 2e + (2u) 33332'22 1779'90 + 813*68 (2) 35923'80 = 47960'42, 50552'00 ; 

 also e + u + (l) 38292-32 815'34 (1)39107-56=49739-60, 50554'94; the former 

 being 177779 above the calculated first line of 47961*81. 



The Value of the Xenon Oun. In the case of xenon the triplet disturbance appears 

 to be small. The result has been obtained that Aj = 24893 = 40f<S and A 2 = 10999 

 = 18(5, giving respectively for 8 the values 610*87, 611*05 or 610'94 from Ai + A 2 . In 

 the preceding 611 has been adopted for S which is sufficiently close except where 

 very large multiples of S are in question. To obtain more accurate values of A 2 

 recourse must be had to the F and D sequences. Incidentally they have already been 

 touched upon, but we are now in a position by a discussion of the whole material to 

 attain a greater exactness. 



Xenon, as has been seen, shows numbers of parallel displaced groups of D and F 

 series, each of which gives data for the determination of A 2 . Unfortunately those 

 lines which might be expected to give the most accurate values are in the ultra-red 

 beyond the observed region, and the process of extrapolation by the v, separation, or 

 by links, leaves a considerable margin of uncertainty owing to the 1780 modification 



