First observation of two hyperfine transitions in antiprotonic 3He

Abstract

We report on the first experimental results for microwave spectroscopy of the hyperfine structure of normalp¯3He+. Due to the helium nuclear spin, normalp¯3He+ has a more complex hyperfine structure than normalp¯4He+, which has already been studied before. Thus a comparison between theoretical calculations and the experimental results will provide a more stringent test of the three-body quantum electrodynamics (QED) theory. Two out of four super-super-hyperfine (SSHF) transition lines of the false(n,Lfalse)=false(36,34false) state were observed. The measured frequencies of the individual transitions are 11.12559(14) GHz and 11.15839(18) GHz, less than 1 MHz higher than the current theoretical values, but still within their estimated errors. Although the experimental uncertainty for the difference of these frequencies is still very large as compared to that of theory, its measured value agrees with theoretical calculations. This difference is crucial to be determined because it is proportional to the magnetic moment of the antiproton.

Microwave spectroscopy measurements of the hyperfine structure in antiprotonic 3He

“…The frequency difference ν th-exp between theory and experiment is ∼ 0.6 MHz for ν HF between the two SSHF lines at 11 GHz is 68 kHz out of 32 MHz. This difference is important due to its proportionality to the magnetic moment of the antiproton [7,20].…”

“…The experimental method and the general design of the setup were the same as for p 4 He + [7,12]. However, a new cryostat with a compressor-based cooling system [13] was built, which led to improvements of the operation and more efficient use of the measurement time.…”

“…Thus the number of annihilations after the second laser pulse will be larger if more antiprotonic atoms were transferred by the microwave pulse. More details on the experimental technique and measurement parameters can be found in [7].…”

“…In order to determine the optimum power to induce an electron spin flip and thus the maximum population transfer between two SSHF states, the signal was tested at several different microwave powers. The ν HF transition at about 7.5 W (for further detail refer to Friedreich et al [7]). …”

Wave packet simulations of antiproton scattering on molecular hydrogen

“…Mixed matter-antimatter many-body systems provide a field of study, which exceeds the pure annihilation effects and allows for comparison with the dynamics of ordinary molecular systems. Examples of such many body systems includes, e.g., antihydrogen-hydrogen 7 , antiprotonic helium 8,9 and various antiproton -gas collisions investigated by the ASACUSA collaboration in the antiproton collisional kinetic energy regime of 2-11 keV 10 . In this work we have investigated the collision an antiproton (p) with molecular hydrogen as a model system for more complex antiparticle -molecular interactions.…”