326 
PROF. C. G. BAKKLA ON X-RAYS AND THE THEORY OF RADIATION. 
which was transformed into K fluorescent (characteristic) radiation ; Table II. the 
fraction of energy of K absorption which re-appeared as K fluorescent radiation. 
Before generalising from these results, we must eliminate all those which are obviously 
unreliable. Thus when the primary radiation was of just shorter wave-length than 
Table II.—Giving Fraction (F K /E K ) of Primary Energy Specially Absorbed—•“ K 
Absorption ”—transformed into Fluorescent X-radiation of Series K. 
Primary radiation. 
Wave-length 
(ai). 
Substance 
exposed to primary radiation. 
Cr. 
Fe. 
Co. 
Ni. 
Cu. 
Zn. 
cm. 
Fe X-radiation (series K) 
1 • 93 x 1CT 8 
0-176 
Co „ ( „ ) 
1-78 x10~ 8 
0-154 
(0 - 504) 1 
Ni „ ( „ ) 
1-65x10~ 8 
0 • 145 
0 • 252 
0-287 1 
Cu „ ( „ ) 
1-54 x10“ s 
0-127 
0-225 
0-305 
0'288 i 
Zn „ ( „ ) 
1•43 x10~ 8 
0-109 
0-207 
0-282 
0-340 
0-358 1 
As „* ( „ ) 
1 • 17 x 1CT 8 
0-0757 
0-150 
0-195 
0-233 
0-288 
0-327 
Se „ ( „ ) 
l-10x 10~ 8 
0-0624 
0-120 
0-149 
0-187 
0-231 
0-278 
Ag » ( » ) 
0-56 x10" 8 
0-062 
(0-118) 
(0-132) 
the fluorescent radiation which it was exciting, the latter appeared in only small 
intensity accounting for from 2 to 10 per cent, of the total absorption (Table I.). 
Owing to this and to the admixture of scattered radiation, the possible percentage 
error was extremely high ; these results expressed in terms of the special K absorption, 
which also being a difference effect is difticult to measure with any accuracy in this 
region, are seen to be irregular and of no value. We must therefore reject these.* 
t> i u 1 ,i r , • K fluorescent radiation (energy) . t n . „ , 
By plotting the fraction —- ; -——r-- f -against wave-length of the 
K. primary absorption (energy) 85 
primary radiation it is seen that the other results are perfectly regular (fig. 4). Of 
the energy of primary radiation absorbed in association with the emission of K 
radiation, the greatest fraction is transformed into K fluorescent radiation when the 
wave-length of the primary ramation differs least from that of the fluorescent 
radiation. As the wave-length of the primary radiation diminishes the fraction so 
* A note of interrogation indicates these in Table II. Reference to the corresponding values in 
Table I. shows them to be based on the experimental determination of small quantities. Their irregularity, 
where all else is regular, is evidence of their unreliability except as indicating orders of magnitude : the 
reason is obvious. If these values could be experimentally determined with accuracy, they would 
probably be quite different from those obtained by the use of a perfectly homogeneous radiation of wave¬ 
length given in column II. Still, this fact would not appreciably affect the conclusions drawn below, 
because the values are compared with corresponding absorptions—that is, with the absorptions of identical 
radiations. 
