Dynamical nuclear polarization (DNP) transfers the polarization of electron spins at cryogenic temperatures to achieve strong nuclear polarization for applications in nuclear magnetic resonance. Recently introduced approaches employ optical pumping of nitrogen-vacancy (NV) centers in diamond to achieve DNP even at ambient temperatures. In such schemes microwave radiation is used to establish a Hartmann-Hahn condition between the NV electron spin and proximal nuclear spins to facilitate polarization transfer. For a single monochromatic microwave driving field, the Hartmann-Hahn condition cannot be satisfied for an ensemble of NV centers due to inhomogeneous broadening and reduces significantly the overall efficiency of dynamical nuclear polarization using an ensemble of NV centers. Here, we adopt generalized Hartmann-Hahn type dynamical nuclear polarization schemes by applying microwave driving fields with (multiple) time-modulated frequencies. We show that it is possible to enhance the effective coupling between an ensemble of NV center spins with inhomogeneous broadening and nuclear spins, thereby improving significantly the overall efficiency of dynamical nuclear polarization. This approach can also be used to achieve dynamical nuclear polarization of an ensemble of nuclei with a distribution of Larmor frequencies, which would be helpful in magnetic resonance spectroscopy using a single NV spin sensor.

中文翻译：

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使用钻石色心的多色控制进行动态核极化

动态核极化（DNP）在低温下传递电子自旋的极化，以实现用于核磁共振的强核极化。最近引入的方法采用光学泵浦金刚石中的氮空位（NV）中心来实现DNP，即使在环境温度下也是如此。在这样的方案中，微波辐射用于在NV电子自旋和近端核自旋之间建立Hartmann-Hahn条件，以促进极化转移。对于单个单色微波驱动场，由于不均匀加宽，无法满足NV中心集合的Hartmann-Hahn条件，并且显着降低了使用NV中心集合的动态核极化的整体效率。这里，我们通过应用具有（多个）时间调制频率的微波驱动场，采用广义的Hartmann-Hahn型动态核极化方案。我们表明，有可能增强NV中心自旋与非均匀展宽和核自旋之间的有效耦合，从而显着提高动态核极化的整体效率。此方法还可用于实现具有拉莫尔频率分布的原子核集合的动态核极化，这将有助于使用单个NV自旋传感器的磁共振波谱。我们表明，有可能增强NV中心自旋与非均匀展宽和核自旋之间的有效耦合，从而显着提高动态核极化的整体效率。此方法还可用于实现具有拉莫尔频率分布的原子核集合的动态核极化，这将有助于使用单个NV自旋传感器的磁共振波谱。我们表明，有可能增强NV中心自旋与非均匀展宽和核自旋之间的有效耦合，从而显着提高动态核极化的整体效率。此方法还可用于实现具有拉莫尔频率分布的原子核集合的动态核极化，这将有助于使用单个NV自旋传感器的磁共振波谱。