Fig. 2: Laser cooling of antihydrogen.
The spectral lineshapes and the TOF distributions, obtained during the probing phase by detecting antihydrogen annihilations resulting from laser-induced spin flips. In all cases, the curves are drawn to guide the eye. a, The experimental lineshapes given by the number of annihilation counts within a TOF time window of 0 to 3 ms, as a function of the probe laser frequency relative to the resonant frequency. b, TOF distributions representing the time between the nanosecond-scale probe laser pulse and the detection of the annihilation. Events with an axial annihilation position between +10 cm and –10 cm are plotted. The distributions are compared for the experimental series given in Table 1: the no-laser series (green); the heating series with a detuning of approximately +160 MHz (blue); the cooling series with a –240-MHz detuning (orange); and the ‘stack and cool’ series where a –230-MHz detuning was applied during both the stacking phase and the cooling phase (red). c, d, The corresponding simulations for the lineshapes (c) and the TOF distributions (d). Each distribution is normalized to its total number of counts, and the error bars represent 1 s.d. counting statistical uncertainties. The values labelled \({\bar{E}}_{{\rm{L}}}\) and \({\bar{E}}_{{\rm{T}}}\) represent the mean of ‘true’ longitudinal and transverse energies, respectively, of the simulated atoms at the time of the spin-flip transitions. See text and Methods.
