Variational calculation of energy levels for metastable states of antiprotonic helium

Recent results of laser spectroscopy experiments of pionic helium atoms at PSI

“…This can help set upper limits on constraints on the muon antineutrino mass by laboratory experiments [13]. Some upper limits may also be set on any exotic force [14][15][16][17][18] that involves the π − , as has been done in the case of antiprotonic helium (pHe + ≡ p + He 2+ + e − ) atoms [19][20][21][22][23][24][25][26][27][28][29][30]. Unlike the pHe + case, the atomic structure of π 4 He + contains no hyperfine structure that arises from the spin-spin interaction between the spin-0 π − and 4 He nucleus [31,32].…”

Recent progress of laser spectroscopy experiments on antiprotonic helium

“…This unusual longevity allows us to measure the transition frequencies ofpHe + by laser spectroscopy. quantum electrodynamics (QED) calculations [4][5][6], the antiproton-to-electron mass ratio Mp/m e can, in principle, be determined with a relative precision of less than 1 × 10 −10 . This may rival the best determinations of the proton-to-electron mass ratio M p /m e obtained from experiments involving Penning traps [7][8][9][10][11] or laser spectroscopy measurements of HD + molecular ions [12,13].…”

“…The metastablepHe + preferentially deexcites by undergoing slow radiative transitions of the type n = = −1 with lifetimes of τ = 1-2 µs. The transition frequencies ofpHe + have been calculated [4][5][6] to a relative precision of approximately 10 −10 by evaluating the complete set of QED corrections up to order m e α 7 in atomic units. Here, m e and α respectively denote the electron mass and the fine structure constant.…”

Single-photon laser spectroscopy of cold antiprotonic helium

“…The atoms are experimentally synthesized via the reaction, p + He → pHe + + e − , which occurs when an antiproton beam [24] is allowed to come to rest in a helium gas target [25][26][27]. The transition frequencies of pHe + spanning the infrared to ultraviolet regions have been calculated [1][2][3] to a relative precision of ∼ 10 −10 by evaluating the QED corrections up to order m e α 7 in atomic units. Here m e and α respectively denote the electron mass and the fine structure constant.…”

“…Here m e and α respectively denote the electron mass and the fine structure constant. The calculations used the International Council for Science Committee on Data for Science and Technology (CODATA) 2010 recommended values of the fundamental constants [28], which included the fine structure constant α, the 3 He-and 4 He-to-electron mass ratios, the Bohr radius, and the Rydberg constant. The corrections to the atomic transition frequencies that arise from the finite charge radii of the helium nucleus (4 to 7 MHz) and of the antiproton [29,30] (< 1 MHz) are small in the case of pHe + , because the spatial overlap between the Rydberg antiproton orbital and the nucleus is relatively small, and because the negatively-charged antiproton is polarized away from the 1s electron in the atom.…”