( 584) 



§ 7. With the spectrometer we found in the ordinary spectnmi of 

 ruby: At 18' strong band 692,4—692,6; very strong band 693.9— 

 694,2; at —193' strong line 691,7; stronger line 693,2. So with 

 decrease of temperature a displacement of 0.7 im takes place towards 

 violet, the mutual distance of the double line retaining the value 

 1.5 nn, however, as it is also found between the centre-lines of 

 the tw^o bands. In the extraordinary spectrum, at 18° band 692,5, 

 fainter band 694,1; at —193° faint line 691,7, fainter line 693,2. 

 In both spectra about 8 more bands of less importance, which cannot 

 all be discussed here. 



In the extraordinary grating spectrum the bands have faded away 

 so much that an exact observation is impossible ; hence only the 

 ordinary spectrum was observed here. Though the bands are not 

 sharply defined, they were estimated at about the same breadth by 

 the two observers, viz. at 18° : band 692.5 at 0.23, band 694,1 at 

 0.33 im. In a longitudinal magnetic field, estimated at about 30 

 kilogauss the breadths amounted to 0,37 resp. 0.49 mi in a situation 

 slightly shifted towards violet ; the increase in breadth was therefore 

 0,14 and 0.16 mi respectively. 



With unpolarised light the phenomena were pretty much the same 

 as the photo shows ; it was obtained on a "Lumiere B-plate" sensitized 

 for red light with alizarin l)lue and nigrosin with an exposition of 20 

 minutes: 1. indicates the position of the ruby bands in the solar 

 spectrum ; 2. those in the arc-lamp spectrum outside the field ; 3. 

 the same in the field. The apparent broadening is evidently caused 

 by a doublet of vaguely outlined bands, as sufficiently appears from 

 the connection with what follows. 



If the ruby was cooled down to about — 193°, band 692,5 appeared 

 to contract to a breadth of about 0,06, band 694,1 to 0,08 iiti. In 

 fact they have then become absorption lines, which though thicker 

 than Fraunhofer lines, are yet no broader than e.g. those of a dense 

 sodium vapour ; by this gradual transition any distinction between 

 absorption bands and lines vanishes. 



In the field an ordinary ZEKMAN-etfect was now observed as follows : 

 line 692,5 resolves into two components at a mean distance of 

 0,25 nn, the space between somewhat less bright than the spectral 

 background; the components of line 694,1 had a distance of 0,35 //,a 

 with a somewhat darker space between ; possibly due to the inter- 

 mediate lines of a quadruplet ; for both a slight displacement 

 towards violet was to be perceived. So the separation at — 193° 

 seems to be greater than the above broadening at 18°. These nume- 

 rical determinations cannot yet be considered as definite or accurate. 



