Fig. 1: Schematic representation of the reactions, setup and experimental protocols used to study RASER activity.
From: Through-bond and through-space radiofrequency amplification by stimulated emission of radiation
a Reaction scheme of pairwise addition of p-H2 to precursors 1'–4' to yield HP products 1–4 (R1–R3 are different substituent groups for propargylic/allylic fragment, see table below the reaction scheme): allyl alcohol (1), allyl pyruvate (2), 3-buten-2-ol (3), 2-methyl-3-buten-2-ol (4) (corresponding precursors are propargyl alcohol (1'), propargyl pyruvate (2'), 3-butyn-2-ol (3'), 2-methyl-3-butyn-2-ol (4')). Red HA and HB atoms stand for parahydrogen-nascent atoms. Magenta letters denote different types of protons in the molecules 1–4. b Scheme of the experimental setup used for RASER experiments. c Schematic event sequences in PR-inside (PASADENA inside the RF-coil RASER), PR-above (PASADENA above the RF-coil RASER), and ALTADENA RASER experiments. 1H NMR signals were acquired for 104 s without the application of any RF excitation pulses.
