Zeeman effect and level identification of As i

Abstract

The Zeeman effect of the neutral arsenic spectrum was observed photographically from 1937 to 11 244 Å. Well-defined Zeeman patterns of 130 As i lines were recorded and yielded 61 Landé g values of which 9 were previously available. The light source was an electrodeless lamp of quartz containing metallic arsenic and helium carrier gas at 3–5 Torr; it was operated in a magnetic field of 24 025 or 10 000 G and excited by a standard microwave generator. Conditions that were favorable for the excitation of the first spectrum of arsenic were noted and characterized. The J and g values obtained from our Zeeman patterns confirmed most of the existing As i analysis but forced reclassification of several terms. There is acceptable agreement between the g values and those calculated from intermediate-coupling wave functions obtained by the least-squares fitting of energy levels for the single configuration approximation to 4s2 4p3 and 4s2 4p2 5s. Also, adequate fits of energy levels could be obtained in the single configuration approximation for each of the 4s2 4p2 5p and 4s2 4p2 6p configurations, but large discrepancies occurred in the g values. Such discrepancies were reduced considerably when configuration interaction was included in the calculations, providing positive evidence of configuration mixing that led to the reclassification of several energy levels and to the addition of some of the missing classifications.