Investigation of Ultrafast Nuclear Spin Polarization Induced by Short Laser Pulses

We theoretically investigate the dynamics of nuclear spin induced by short laser pulses and show that ultrafast nuclear spin polarization can take place. Combined use of the hyperfine interaction together with the static electric field is the key for that. Specifically we apply the idea to unstable isotopes, ${}^{27}\mathrm{Mg}$ and ${}^{37}\mathrm{Ca}$, with nuclear spin of $1/2$ and $3/2$, respectively, and show that 88% and 62% of nuclear spin polarization can be achieved within a few to tens of ns, which is 2–3 orders of magnitude shorter than the time needed for any known optical methods. Because of its ultrafast nature, our scheme would be very effective not only for stable nuclei but also unstable nuclei with a lifetime as short as $\mu \mathrm{s}$.

Figure 1

Level scheme for the $I=1/2$ system of alkaline-earth atoms in the (a) coupled basis and (b) uncoupled basis descriptions.

Figure 2

Variation of the (a) degree of nuclear spin polarization and (b) probability in each nuclear spin state as a function of time for the ${}^{27}\mathrm{Mg}$ $3s^2$ ${}^{1}S_0-3s6p$ ${}^{1}P_1$ ($I=1/2$) system under the application of a $3\mathrm{kV}/\mathrm{cm}$ static electric field. In graph (b), solid and dashed lines represent probabilities in the $m_I=\pm 1/2$ nuclear spin states, respectively.

Figure 3

Level scheme for the $I=3/2$ system of alkaline-earth atoms in the coupled basis.

Figure 4

Variation of the (a) degree of nuclear spin polarization and (b) probability in each nuclear spin state as a function of time for the ${}^{37}\mathrm{Ca}$ $4s^2$ ${}^{1}S_0-4s6p$ ${}^{1}P_1$ ($I=3/2$) system under the application of a $3\mathrm{kV}/\mathrm{cm}$ static electric field. In graph (b), solid, dot-dashed, long dashed, and dashed lines represent probabilities in the $m_I=\pm 3/2$ and $m_I=\pm 1/2$ nuclear spin states, respectively.