The band spectra associated with zinc, cadmium, and mercury

Tbe band spectra of the alkali metals are now well known, and it has been established that they are due to a small proportion of diatomic molecules, which are normally present in the vapours of these metals. It is as yet uncertain how many other metals, with vapours which, according to the ordinary methods of measurement, appear to be monatomic, give similar spectroscopic proof of association. Throughout a large number of experiments with the saturated vapours of the alkaline earth elements, up to 1200° C., we have found no evidence of band spectra which can be attributed to diatomic molecules of these metals. The elements of Group II b of the Periodic Table are much more interesting in this respect, and it is with experiments on the absorption spectra of these that this communication is concerned.