Simultaneous Heteronuclear ¹H and ¹³C RASER's Driven by Parahydrogen-Induced Polarization

Nuclear spin masers (aka RASERs) offer a window into mesoscopic quantum systems, bridging microscopic quantum mechanics and macroscopic collective dynamics. RASERs are frequently encountered in nuclear magnetic resonance (NMR) experiments using samples containing unusually large magnetization or highly polarized spin ensembles. RASERs emerge when the spin ensemble becomes strongly coupled to a resonator (the NMR detection coil) and collective emission is enslaved by the resonator mode. Here we demonstrate the first simultaneous, heteronuclear ¹H and ¹³C RASER from a single molecule, [1-¹³C]ethyl-acetate. Unlike previous heteronuclear RASERs, as obtained from ³He-¹²⁹Xe mixtures, in this work the RASER signals arise from spins within the same molecule exhibiting significant scalar J-couplings between the two nuclear spins. The system is driven by parahydrogen-induced polarization and observed using direct sampling with dual-channel acquisition, enabling direct digital strategies and further insight towards NMR cavity control. We observe complex, competitive dynamics between the two RASERs. This work provides an avenue for investigating heteronuclear interactions in strongly coupled spin systems and developing novel resonator-mediated feedback and control schemes.