Bands in the secondary spectrum of hydrogen-II

Abstract

In a previous communication, evidence has been given for the existence of an extensive system of bands of a distinctive type, extending over a wide range of the visible and infra-red spectrum of hydrogen. These are called in the writers’ notation the “Type-II Bands,” and are characterised by parallel groups of Q series, each group comprising from three to five bands. The individual bands of a group are spaced out at intervals of very nearly 92 wave-numbers, the spacing being in some cases approximately constant and in some cases varying in such a way as to indicate that the null lines of the group are given by a quadratic law. For certain bands P and R series have also been identified obeying the Simple Combination Principle. All such series are closely parallel to the corresponding branches pf a band (II A , a ) described by one of us, which comes out strongly in an arc struck between tungsten electrodes in an atmosphere of hydrogen at higher pressures. The Type-II Bands have for various reasons been ascribed to triatomic hydrogen, H 3 . In the present paper, our purpose is to extend the study of these regularities. We begin by giving a group occurring in the green, which bears a strong resemblance to the infra-red groups described in detail previously.