The Band Spectrum of Boron Nitride

Abstract

DR. R. S. MULLIKEN has described in three letters his recent work on the application of the quantum theory of band spectra to the study of isotopy. In the first of these letters (Science, vol. 58, p. 164, August 31, 1923) he establishes the isotope effect in the case of boron by the analysis of my data for a band spectrum which I had shown to be due to a nitride of boron (Roy. Soc. Proc., A, vol. 91, p. 120, 1915). At the time he accepted this attribution. Since then, however, Dr. Mulliken has undertaken a new experimental investigation and obtained data, a theoretical consideration of which has induced him to ascribe the spectrum to BO rather than to BN, although, as he states in the second letter (NATURE, vol. 113, p. 423, March 22, 1924), “the possibility of BN is not yet altogether excluded”. Apart from this passage, the letter and its title (in which the band spectrum is called that of boron monoxide) leave the impression that in Dr. Mulliken's view the possibility of BN is definitely excluded, an impression which finds later justification in the third letter (NATURE, vol. 113, p. 489, April 5, 1924), where it is stated that “In the case of the BO bands, it was in fact the magnitude of the observed isotope effect which first definitely indicated that they were not due to BN as formerly supposed”.