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. 2021 Jul 6;12(27):6341–6347. doi: 10.1021/acs.jpclett.1c01447

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© 2021 The Authors. Published by American Chemical Society

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(a) Q-band TR-EPR spectrum of a D⁺-χ-A^–-Q system (sketched on top) with the chiral axis aligned parallel to the external field (integrated from 100 to 300 ns) and for different initial states of the radical pair (with the qubit always in |↓⟩): singlet (blue line), corresponding to transfer along a linear bridge without CISS effect; fully polarized state (on both donor and acceptor, red); unpolarized state |ψ_U⟩ as suggested in ref (32), black. The gray-shaded area represents the signal from the donor–acceptor, while at larger field the absorption peaks are due to the qubit. (b) NMR spectrum as a function of frequency, probing nuclear excitations on a nuclear spin 1/2 (e.g., a ¹⁹F, Larmor frequency ν_L ≈ 40 MHz at 1 T) coupled by hyperfine interaction to the donor. The different intensity of the two peaks for p = 0 is due to different matrix elements for the two transitions. Variance from the p = 0 behavior directly measures the acceptor polarization. Parameters: hν = 34 GHz, J_AQ^z ≈ 200 MHz, r_DA = 25 Å, r_AQ = 8 Å, = 10 MHz, g_1,2 = g_e ∓ Δg/2, with Δg = 0.002, g_Q = (1.98, 1.98, 1.96), as typical for VO²⁺ or Ti³⁺,⁴²T₁ = 2 μs, T₂ = 0.5 μs, and T_R = 10 μs. Inhomogeneous broadening of the parameters is included by a Gaussian broadening of the peaks with fwhm 2.35 mT. To generalize our analysis, we did not include parameters of a specific qubit, such as hyperfine interaction.

Inline graphic — (a) Q-band TR-EPR spectrum of a D⁺-χ-A^–-Q system (sketched on top) with the chiral axis aligned parallel to the external field (integrated from 100 to 300 ns) and for different initial states of the radical pair (with the qubit always in |↓⟩): singlet (blue line), corresponding to transfer along a linear bridge without CISS effect; fully polarized state (on both donor and acceptor, red); unpolarized state |ψ_U⟩ as suggested in ref (32), black. The gray-shaded area represents the signal from the donor–acceptor, while at larger field the absorption peaks are due to the qubit. (b) NMR spectrum as a function of frequency, probing nuclear excitations on a nuclear spin 1/2 (e.g., a ¹⁹F, Larmor frequency ν_L ≈ 40 MHz at 1 T) coupled by hyperfine interaction to the donor. The different intensity of the two peaks for p = 0 is due to different matrix elements for the two transitions. Variance from the p = 0 behavior directly measures the acceptor polarization. Parameters: hν = 34 GHz, J_AQ^z ≈ 200 MHz, r_DA = 25 Å, r_AQ = 8 Å, = 10 MHz, g_1,2 = g_e ∓ Δg/2, with Δg = 0.002, g_Q = (1.98, 1.98, 1.96), as typical for VO²⁺ or Ti³⁺,⁴²T₁ = 2 μs, T₂ = 0.5 μs, and T_R = 10 μs. Inhomogeneous broadening of the parameters is included by a Gaussian broadening of the peaks with fwhm 2.35 mT. To generalize our analysis, we did not include parameters of a specific qubit, such as hyperfine interaction.