152 0. C. Lester — Oxygen Absorption Bands. 



Relations between Lines and Lands. 



The terms " head " and " tail " or " train " used to designate 

 the two parts of the A, B, and a groups cannot be taken in 

 this case in the usual sense of these terms as applied to band 

 spectra, and are really misnomers. The spectrum is composed 

 of two series of entirely separate bands instead of a single 

 series, the so-called " heads " forming the first and the " tails " 

 the second. The first series has the appearance of being nearly 

 all " head " and the second all " tail," but the apparent crowd- 

 ing and confusion in the case of the former is due to the dis- 

 tance between the first few pairs being less than their width. 

 That the "head" and "tail" are really separate bands is 

 apparent from the following considerations. 



Both "head " and " tail" begin with pairs of the same width, 

 which decrease in width with increasing wave length in the 

 same manner. 



No series in a " head " or " tail " is a continuation of a series 

 in the other as it should be if they were parts of the same 

 band. Also, the first and second differences between homolo- 

 gous lines in the " heads " and " tails " form entirely different 

 series as do the ratios of the homologous lines. Further, while 

 there are no lines in places calculated for the tail series extended 

 upward, faint lines appear to be in the proper places for an 

 extension of the head, just as if the first band, instead of 

 fading out gradually as the second does, should drop very sud- 

 denly in intensity on approaching the region occupied by the 

 second. That this is apparently what happens is indicated 

 also by the fact that the last line of what is usually considered 

 the last pair in the " head " of B is scarcely half the intensity 

 of its mate and in a is less than half. Extending the series of 

 the first bands of B and a we find the following agreement 

 between observed and calculated values. 



Observed. 



Calculated. 



6879-28 | „ 

 80-17 j 











81-80 



81-85 



82-72f 



82-72 



84-65 



84-67 



85-54 



85-52 



87-75 



87-74 



88-60 



88-57 



91-05 



91-06 



91-87 



91-87 



94-67 



94-63 



95-50 



95-42 



Observed. Calculated. 



6284-00)* 



84-75 C 



86-09 ' 86-11 

 86-88 86-84 

 88-48 88-49 

 89-20 89-20 

 91*14 (covered) 91*14 

 91-83 



* Last pair of strong lines. f Hidden by heavy adjacent line. 



