ATOMIC-BEAM MEASUREMENT OF ISOTOPE SHIFTS IN D1 LINE OF 127CS 129CS 133CS 134MCS 134CS AND 137CS

The atomic-beam method has been applied to the measurement of isotope shifts in the D1 line of five radioactive isotopes including the isomeric pair Cs134-Cs134m. The shifts in these lines, relative to the energy in the D1 line of Cs133 are as follows: Cs127, +5.9(1.5) mK; Cs129, +2.8(1.5) mK; Cs134, +1.8(1.0) mK; Cs134m, -2.2(1.2) mK; and Cs137, -6.0(1.5) mK. Here a positive sign means that the frequency of the D1 line for the indicated isotope is greater than that for Cs133. Evidence is presented which indicates that the observed shifts arise almost completely from nuclear effects. These shifts must therefore be compared with a calculated shift arising from the normal volume effect of 10 mK/neutron. © 1969 The American Physical Society.