The hyperfine structure of the 7p 2P1/2, 3/2 levels of 115in and the 5p 2p1/2 level of 2VA1 has been measured using high-resolution laser spectroscopy on atomic beams. For the magnetic-dipole and electric-quadrupole interaction constants, a and b, the following values were obtained; a(7p 2Pa/2)=90.7(10 ) MHz, a(7p 2P3/2)=32.3(2 ) MHz and b (7p 2P3/2)= 24.5 (1.5) MHz for 11Sin and a (5p 2P1/2)= 20 (2) MHz for 27A1. Many-body calculations on 2p states in aluminum, gallium and indium have also been performed.

The specific mass shift of the ionisation energy between 20Ne and 22Ne has been calculated using many-body perturbation theory. The first-order expectation value, neglecting relaxation effects is -41.0 GHz. Allowing for relaxation effects changes the result to -16.3 GHz, which, together with a lowest-order correlation effect of 9.3 GHz, gives a total result of -7.0 GHz. The experimental value is (-11 ± 3) GHz and the discrepancy is ascribed to higher-order correlation effects, which have not been evaluated.

Doppler-free two-photon laser spectroscopic measurements in the deep red spectral region have been performed on the transition 42Sx/z---~42Dj in the naturally abundant isotopes 39 and 41 of atomic potassium. The 4D level isotope shift, -81 _+ 12 MHz was obtained by combining the current results with data from Rydberg-state spectroscopy. Many-body perturbation theoretical calculations of the specific mass shift in the measured state are also presented. With the use of Brueckner orbitals the value -70 MHz was obtained in substantial agreement with the experimental result.