Alternating Delays Achieve Polarization Transfer (ADAPT) to heteronuclei in PHIP experiments.

A new methodology for producing hyperpolarized 13C nuclei in small organic systems via parahydrogen induced polarization (PHIP) is proposed: ADAPT (Alternating Delays Achieve Polarization Transfer). The theoretical foundation of the process is investigated in some detail and experimental examples demonstrating the viability of the approach are provided as well. The number of adjustable parameters is fewer than most of other conversion schemes. The achieved theoretical heteronuclear polarization is close to unity for any examined magnetic equivalence regime. The duration of the pulse sequence, which was successfully implemented, can be shorter than other established methods reducing possible relaxation losses. The conversion scheme is robust to B1 inhomogeneities, but more sensitive to off-resonance RF irradiation.