The Spin and Magnetic Moment of the Rhodium Nucleus

NATURALLY occurring rhodium consists almost entirely of one isotope, 45 Rh 103 . No hyperfine structure has previously been found, nor has a determination of the nuclear spin by any other method been made. By passing light from a hollow-cathode tube containing rhodium through an atomic beam of rhodium, we were able to observe absorption in one of the resonance lines, 3434.90 A. (4 d 8 5 s 4 F 9/2 – 4 d 8 5 p 4 G 11/2 ) 1 . The absorption spectrum shows a well-resolved doublet, of splitting 0.023 cm. −1 . This proves conclusively that the nuclear spin has the value I = ½, since any other value would produce a quartet or higher multiplet. The splitting of the line must be attributed to the ground-term, which contains an unpaired s -electron. If perfect Russell–Saunders coupling is assumed, the value of the magnetic moment can be calculated by means of the conventional approximation methods. It is found to be − 0.11 nuclear magnetons. This is one of the smallest magnetic moments so far reported.