The nuclear moment of the indium atom

Abstract

The investigation described here is a continuation of an earlier one carried out by two of the authors in which certain lines in the first spark spectrum of indium were studied and the conclusion drawn that the nuclear moment of that atom was probably ½ h /2π. During the time that elapsed between the completion of this work and its publication there appeared a paper by Jackson describing an examination of certain lines in the arc spectrum which led to an I value of unity. Two of the lines λ4511, λ4102 observed by him had appeared on our plates and been measured by us, the structure recorded in the two cases being quite different. In proceeding with the research it was therefore decided first to revise the work on these lines and then to direct our attention to lines in the ultra-violet region of the arc spectrum. The discharge tube used was very similar to Jackson’s. It was made from quartz and consisted of two wide portions 8 cm. in length and 2·5 cm. in diameter joined by a narrower one 4 cm. in length and 0·8 cm. in diameter. The electrodes were made of sheet copper wrapped around the wide parts of the tube and were coupled inductively to an oscillating circuit with a frequency range of 10,000 to 14,000 cycles. Two U. V. 861 General Electric screen grid radio frequency power amplifier tubes operating in parallel were used. A small amount of indium trichloride (Hilger’s H. S. brand) was introduced into the tube, which was then evacuated. It was usually necessary to heat the tube slightly by means of a bunsen to start the discharge, but once this was done no further heating was necessary.