﻿656 Emission Spectrum of Monatomic Iodine Vapour. 



at 650° C. one of the two characteristic lines 3281 A appeared;, 

 the second strong line 3384 A appeared later ; at 800° C. it 

 was yet faint. The manner of producing the spectra seemed 

 to be of no influence : I observed the same phenomena 

 whether applying uncondensed discharges of a Ruhmkorff 

 coil provided with the hammer interruptor, or with the 

 Oudin high-frequency transformer, acuated by an electrolytic 

 interruptor. 



I determined the wave-lengths of the main lines of the 

 spectrum observed ; they were found to be 4868. .4769, 

 4680, 4324, 4132, 4100, 3384, 3281, 3081, 2879, 2593,2583, 

 2566 A. My spectrograph had a dispersion insufficient for 

 accurate work. The error of the determinations should not 

 exceed 2-3 A for the fainter lines, and 1A for the tv.o 

 stronger ones*. 



It would be difficult to tell whether all these lines are 

 absolutely new, or whether some of them can be found in 

 the ordinary line spectrum of iodine : the exactness of my 

 measurements is insufficient, taking into account that the 

 lines of iodine are exceedingly numerous; happily there are 

 no lines of the ordinary spectrum in the proximity of 

 3281 A; that characteristic line is thus certainly a new one. 



III. Results. 



A new line spectrum of iodine was observed, and wave- 

 lengths of the main lines approximately determined. This 

 spectrum belongs evidently to the atom of iodine ; it appeared 

 more and more distinctly with increase of the dissociation 

 of iodine molecules ; at the same time the band spectrum 

 disappeared. The band spectrum of iodine seems thus to be- 

 inherent in the molecule. It was found that the band 

 spectrum possessed in the ultra-violet a very regular structure,, 

 contrary to that which had hitherto been imagined. 



It may be permitted to the Author to express here his best 

 thanks to Prof. S. Pienkowski, who in a most generous way 

 has supplied him with a quartz spectrograph. 



A great part of the expense was covered by the Mianowski 

 Foundation. 



Warsaw, Physical Laboratory of the 



State Technical School, founded 

 "by H. Wawelberg and S. Rotwand. 

 May 1922. 



* In the violet part of the spectrum much greater errors are possible,, 

 the dispersion of the quartz prisms being there very small. While this 

 paper was in the press some other lines were measured and the following 

 wave-lengths found : 4640, 4414, 4217, 3576. 2528, 2524, 2516, 2507. 



