Spin polarization of Doppler-broadened atoms by the broadband nanosecond and transform-limited picosecond laser pulses: case study for the muonium

Abstract

We study the spin polarization of Doppler-broadened atoms by broadband nanosecond (ns) pulses, and compare the polarization efficiency with that by the transform-limited picosecond (ps) pulses that have the same spectral bandwidth. Specific calculations are performed for the case of muonium with a set of density matrix equations and with rate equations using the uncoupled basis states. We find that the polarization efficiency with the broadband ns laser pulses is rather good, although it is not as good as that with the transform-limited ps pulses. Our results imply that, depending on the available laser system, we can use either broadband ns or transform-limited ps laser pulses to polarize almost any Doppler-broadened atoms.

Muon cooling at J-PARC

“…Using six pieces of the targets and five times more laser energy, the USM flux increases three times more. Optical pumping of muonium is also proposed to increase the spin polarization of the USM [13]. It is calculated that the spin polarization can be as high as 80% after optical pumping using a pulse train of circularly polarized light at 122 nm.…”

Effective collinear optical pumping for nuclear spin polarization

“…However, a subset of atoms fulfilling the CPT condition can exist and a longer interaction time is required to achieve higher polarization. Recently Nakajima has proposed that a sequence of short laser pulses with a very broad spectral bandwidth can efficiently polarize nuclear spin of atoms within a very short time scale especially for muonium [14][15][16].…”