2025/09/28 by Jóźwiak, Hubert J., Bakalov, Dimitar, Przybytek, Michał +2
#Atomic Physics (physics.atom-ph) #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Quantum Physics (quant-ph)
paper · doi:10.48550/arxiv.2509.23854
We present the first fully ab initio calculations of collision-induced broadening and shift of spectral lines in antiprotonic helium (pHe+) perturbed by atomic helium. To overcome critical limitations of previous studies, we construct a new highly accurate potential energy surface (PES) that spans a wide range of pHe+-He geometries relevant to all metastable states of the exotic helium atom. Rigorous quantum scattering calculations performed using the new PES yield scattering S-matrices from which we extract pressure broadening and shift coefficients for 50 transitions in antiprotonic helium-4 (p4He+). This dataset provides the first rigorous benchmark for earlier semiclassical calculations and establishes a robust theoretical reference for high-precision spectroscopy of antiprotonic helium, which is used to test the fundamental charge, parity, and time reversal (CPT) symmetry. The results extend to temperatures relevant to non-gaseous phases of helium, supporting a new class of precision measurements. This study introduces a methodological framework for future investigations of other exotic systems, such as pionic or kaonic helium atoms, enabling the development of reference data for high-precision spectroscopy of these species - an essential component for improving the determination of the pion and kaon masses.