The series spectrum of ionised carbon (C II)

Abstract

For the development of the theory of atomic structure there would appear to be a special need for data relating to the series spectra of the lighter elements. It has, therefore, been thought desirable to publish the present account of the series of singly-ionised carbon without waiting for the completion of the investigation of the spectrum at other stages of ionisation. It is an essential feature of Bohr's quantum theory of spectra that while the series constant for neutral atoms is nearly the same as that for hydrogen, the value of this constant will be increased four times when the atom is singly ionised, nine times when it is doubly ionised, 16 times when it is trebly ionised, and so on. Evidence that a system of series represents a particular stage of ionisation is thus to be sought in the value of the series constant for the system in question. Experimental confirmation has been obtained as far as the second ionisation by Paschen in the case of aluminium,* and as far as the third ionisation by the present writer in the case of silicon.