  A free-induction-decay (FID) type optically-pumped rubidium atomic
magnetometer driven by a radio-frequency (RF) magnetic field is presented in
this paper. Influences of parameters, such as the temperature of rubidium vapor
cell, the power of pump beam, and the strength of RF magnetic field and static
magnetic field on the amplitude and the full width at half maximum (FWHM) of
the FID signal, have been investigated in the time domain and frequency domain.
At the same time, the sensitivities of the magnetometer for the single-pass and
the triple-pass probe beam cases have been compared by changing the optical
path of the interaction between probe beam and atomic ensemble. Compared with
the sensitivity of ~21.2 pT/Hz^(1/2) in the case of the single-pass probe beam,
the amplitude of FID signal in the case of the triple-pass probe beam has been
significantly enhanced, and the sensitivity has been improved to ~13.4
pT/Hz^(1/2). The research in this paper provids a reference for the subsequent
study of influence of different buffer gas pressure on the FWHM and also a
foundation for further improving the sensitivity of FID rubidium atomic
magnetometer by employing a~polarization-squeezed light as probe beam, to
achieve a sensitivity beyond the photo-shot-noise level.
