Fig. 3: Numerical simulation.
From: Cooling positronium to ultralow velocities with a chirped laser pulse train
a, Velocity distribution of Ps. We set the duration of the cooling pulse train to 100 ns, as in the experiment. The one-dimensional velocity distributions of 1S Ps expected at 0, 42, 89 and 127 ns after the beginning of the cooling pulse train are shown. The probability density at each velocity was plotted relative to that at 0 ns. The recoil velocity vr and velocity width Δvsingle (in resonance with the FWHM frequency width of a single pulse in the cooling laser) are also shown. b, Reconstructed fractional change in Doppler profile at 125 ns. The curve shows the simulated results. The thickness originates from the frequency resolution and uncertainty in the uncooled fraction. The filled circles are obtained from Fig. 2b.
