Density shift and broadening of transition lines in antiprotonic helium

The density shift and broadening of the transition lines of antiprotonic he lium have been evaluated in the impact approximation using an interatomic p otential calculated ab initio with the symmetry-adapted perturbation theory . The results help to remove an uncertainty of up to 10 ppm in the laser sp ectroscopy data on antiprotonic helium and are of importance in experimenta l tests of bound state QED and CPT invariance.