We have developed a theoretical description of the evolution of ground state coherences between magnetic sublevels in Rb vapor in the presence of a magnetic field along an arbitrary direction. This formalism uses a rotation matrix approach to describe the evolution of coherences created by two traveling wave laser pulses with orthogonal polarizations. The effect of a magnetic field can be described as a time-dependent rotation of the atomic system about the quantization axis. Predictions based on this theoretical formalism for the functional form of Larmor oscillations in a magnetic field are studied using a coherent transient effect known as magnetic grating free induction decay (MGFID) using room temperature vapor and laser cooled atoms. We find the theoretical predictions to be in excellent agreement with data. The velocity distribution of the cold sample measured from the dephasing time of the MGFID in the absence of magnetic fields is in agreement with the sample temperature obtained by imaging the ballistic expansion of the trapped cloud. By using rate equations to model atomic coherences, it is also possible to predict the evolution of magnetic grating echoes (MGE) in a magnetic field. We compare these predictions with experiments from cold atoms and discuss applications of the MGFID and MGE that relate to a precision measurement of the atomic $g$ factor ratio using $^{85}\mathrm{Rb}$ and $^{87}\mathrm{Rb}$ isotopes.We have developed a theoretical description of the evolution of ground state coherences between magnetic sublevels in Rb vapor in the presence of a magnetic field along an arbitrary direction. This formalism uses a rotation matrix approach to describe the evolution of coherences created by two traveling wave laser pulses with orthogonal polarizations. The effect of a magnetic field can be described as a time-dependent rotation of the atomic system about the quantization axis. Predictions based on this theoretical formalism for the functional form of Larmor oscillations in a magnetic field are studied using a coherent transient effect known as magnetic grating free induction decay (MGFID) using room temperature vapor and laser cooled atoms. We find the theoretical predictions to be in excellent agreement with data. The velocity distribution of the cold sample measured from the dephasing time of the MGFID in the absence of magnetic fields is in agreement with the sample temperature obtained by imaging the ballistic expansion of the trapped cloud. By using rate equations to model atomic coherences, it is also possible to predict the evolution of magnetic grating echoes (MGE) in a magnetic field. We compare these predictions with experiments from cold atoms and discuss applications of the MGFID and MGE that relate to a precision measurement of the atomic $g$ factor ratio using $^{85}\mathrm{Rb}$ and $^{87}\mathrm{Rb}$ isotopes.

Physical Review ASep 17, 200811 citations

Experiments with trapped atoms

David E. Pritchard

Massachusetts Inst. of Tech. ReportApr 1, 19910 citations

Magnetic grating echoes from laser-cooled atoms

Anantharaman Kumarakrishnan, S. B. Cahn, Unyob Shim +1 more

We have used two sets of orthogonally polarized traveling-wave pulses separated in time to establish and, subsequently, rephase a spatially periodic coherence grating between the magnetic sublevels of the $F=3$ ground state in a cloud of laser-cooled ${}^{85}\mathrm{Rb}$ atoms. The rephasing results in a magnetic grating echo (MGE). We have used the shape of the signals to determine both transverse and longitudinal velocity distributions and to study the effects of magnetic fields. The amplitude of the MGE with counterpropagating pulses is modulated at the atomic recoil frequency, a consequence of matter wave interference.We have used two sets of orthogonally polarized traveling-wave pulses separated in time to establish and, subsequently, rephase a spatially periodic coherence grating between the magnetic sublevels of the $F=3$ ground state in a cloud of laser-cooled ${}^{85}\mathrm{Rb}$ atoms. The rephasing results in a magnetic grating echo (MGE). We have used the shape of the signals to determine both transverse and longitudinal velocity distributions and to study the effects of magnetic fields. The amplitude of the MGE with counterpropagating pulses is modulated at the atomic recoil frequency, a consequence of matter wave interference.

Physical Review ANov 1, 199820 citations

g

factor ratio using

^{85}\mathrm{Rb}

and

^{87}\mathrm{Rb}

isotopes.

F=3

ground state in a cloud of laser-cooled

{}^{85}\mathrm{Rb}

atoms. The rephasing results in a magnetic grating echo (MGE). We have used the shape of the signals to determine both transverse and longitudinal velocity distributions and to study the effects of magnetic fields. The amplitude of the MGE with counterpropagating pulses is modulated at the atomic recoil frequency, a consequence of matter wave interference.