TY - JOUR

T1 - Quantitative analysis of cross-talk in partly deuterated samples of nuclear spins hyperpolarized by dynamic nuclear polarization (DNP) in the thermal mixing regime

AU - Rodin, Bogdan A

AU - Thalakottoor, Vineeth

AU - Baudin, Mathieu

AU - Birilirakis, Nicolas

AU - Bodenhausen, Geoffrey

AU - Yurkovskaya, Alexandra V

AU - Abergel, Daniel

N1 - We acknowledge the Ministry of Science and Education of the Russian Federation (“Mega” Grant no. 075-15-2021-580). This research was funded, in whole or in part, by the Agence Nationale pour la Recherche (ANR), Grant ANR-22-CE29-0006-01 – DynNonlinPol.

PY - 2023/5/31

Y1 - 2023/5/31

N2 - Dynamical nuclear polarization (DNP) is a powerful method that allows one to polarize virtually any spin-bearing nucleus by transferring electron polarization by microwave irradiation of the electron Zeeman transitions. Under certain conditions, the DNP process can be described in thermodynamical terms using the thermal mixing (TM) model. Different nuclear species can exchange energy indirectly through their interactions with the electron spins and reach a common spin temperature. Such "cross-talk" effects can occur between proton (H) and deuterium (D) nuclei in de- and re-polarization experiments. In this work, we investigate such effects experimentally, using either protonated or deuterated TEMPOL radicals as polarizing agents. An analysis of these experiments based on Provotorov's equations allows one to extract the relevant kinetic parameters, such as the rates of energy transfer between the different reservoirs, and the heat capacity of the non-Zeeman (NZ) electron reservoir, while the heat capacities of the proton and deuterium reservoirs can be estimated based on their usual expressions. These parameters allow one to make predictions of the behaviour of heteronuclei such as carbon-13 or phosphorous-31, provided that their heat capacities are negligible. Finally, we present an experimental study of the dependence of Provotorov's kinetic parameters on the TEMPOL concentration and on the H/D ratio, thus providing insight into the nature of "hidden" spins that are not observable directly because of their proximity to the radicals.

AB - Dynamical nuclear polarization (DNP) is a powerful method that allows one to polarize virtually any spin-bearing nucleus by transferring electron polarization by microwave irradiation of the electron Zeeman transitions. Under certain conditions, the DNP process can be described in thermodynamical terms using the thermal mixing (TM) model. Different nuclear species can exchange energy indirectly through their interactions with the electron spins and reach a common spin temperature. Such "cross-talk" effects can occur between proton (H) and deuterium (D) nuclei in de- and re-polarization experiments. In this work, we investigate such effects experimentally, using either protonated or deuterated TEMPOL radicals as polarizing agents. An analysis of these experiments based on Provotorov's equations allows one to extract the relevant kinetic parameters, such as the rates of energy transfer between the different reservoirs, and the heat capacity of the non-Zeeman (NZ) electron reservoir, while the heat capacities of the proton and deuterium reservoirs can be estimated based on their usual expressions. These parameters allow one to make predictions of the behaviour of heteronuclei such as carbon-13 or phosphorous-31, provided that their heat capacities are negligible. Finally, we present an experimental study of the dependence of Provotorov's kinetic parameters on the TEMPOL concentration and on the H/D ratio, thus providing insight into the nature of "hidden" spins that are not observable directly because of their proximity to the radicals.

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85160407529&origin=inward&txGid=9823b0f2b31f858463bf20f6030d250d

UR - https://www.mendeley.com/catalogue/84409c90-8058-32df-a130-9c1f8693406d/

U2 - 10.1039/d3cp00453h

DO - 10.1039/d3cp00453h

M3 - Article

C2 - 37218287

VL - 25

SP - 15040

EP - 15051

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

IS - 21

ER -