Multinuclear Detection of Nuclear Spin Optical Rotation at Low Field

Abstract

We describe the multinuclear detection of nuclear spin optical rotation (NSOR), an effect dependent on the hyperfine interaction between nuclear spins and electrons. Signals of H andF are discriminated by frequency in a single spectrum acquired at sub-millitesla field. The simultaneously acquired optical signal along with the nuclear magnetic resonance signal allows the calculation of the relative magnitude of the NSOR constants corresponding to different nuclei within the sample molecules. This is illustrated by a larger NSOR signal measured at the F frequency despite a smaller corresponding spin concentration. Second, it is shown that heteronuclear J-coupling is observable in the NSOR signal, which can be used to retrieve chemical information. Multinuclear frequency and J resolution can localize optical signals in the molecule. Properties of electronic states at multiple sites in a molecule may therefore ultimately be determined by frequency-resolved NSOR spectroscopy at low field.

Dynamic Nuclear Polarization Enhanced Nuclear Spin Optical Rotation

“…The dilution factor was estimated based on previous measurements using spectrophotometry, [13] but is not used in the NSOR calculation. Despite the large dilution factor and much shorter pathlength, the SNR was 6.1, about 33 times higher per scan than in the previous NSOR measurement where a 1:1 TFE/water mixture was pre‐polarized with a superconducting magnet [3] . The NMR signal of 19 F was simultaneously acquired (Figure 2 b) for calculations of the nuclear‐spin polarization level and the NSOR constant.…”

“…Based on Equation 1, and knowing the NSOR constant (41.2 mrad M À1 cm À1 ) from ref. [3], the effective light path length was calculated to be l = 3.43 AE 0.38 cm, which is shorter than the internal optical cell length due to effects of flow and mixing (see also a flow simulation in Supporting Information). [3] Assuming this pathlength l, the NSOR constant of DMSO was calculated to be 4.0 AE 0.7 mrad M À1 cm À1 .…”

“…Observation of the nuclear spin optical rotation (NSOR) effect [1] and related magneto-optic nuclear-spin (MONS) phenomena would offer the possibility of probing excited electronic states with local nuclear markers, either by chemical shift, J-coupling, or multi-nuclear labeling. [2,3] The NSOR effect is the only experimentally measured MONS phenomenon so far. Other MONS effects such as the nuclear spin induced Cotton-Mouton effect [4] and nuclear spin circular dichroism [5] have been only theoretically estimated.…”

“…Despite the large dilution factor and much shorter pathlength, the SNR was 6.1, about 33 times higher per scan than in the previous NSOR measurement where a 1:1 TFE/water mixture was prepolarized with a superconducting magnet. [3] The NMR signal of 19 F was simultaneously acquired (Figure 2 b) for calculations of the nuclear-spin polarization level and the NSOR constant. These calculations are described below.…”

Dynamic Nuclear Polarization Enhanced Nuclear Spin Optical Rotation

“…Based on Equation (1), and knowing the NSOR constant (41.2 μrad M −1 cm −1 ) from ref. [3], the effective light path length was calculated to be l =3.43±0.38 cm, which is shorter than the internal optical cell length due to effects of flow and mixing (see also a flow simulation in Supporting Information) [3] …”