The Use of Selective Hole Burning in EPR Spectra to Study Spectral Diffusion and Dipolar Broadening

Pulsed High-Frequency EPR

“…In these cases the distortions by forbidden transitions and the excitation field strength B) are reduced. Hole burning experiments (Dzuba et at., 1993) as FORTE (Willer and Schweiger, 1994) or FT-EPR detected NMR (Wacker and Schweiger, 1991) can also be used at high fields if the strongly prolonged time to drive forbidden EPR transitions is still smaller than the phase memory time T 2. The spectrally resolved G-tensor powder pattern can be used in a positive sense to obtain orientation dependent information on anisotropic interactions, such as hyperfine coupling, dipolar couplings to other close by paramagnetic molecules or anisotropic molecular reorientations.…”

Matrix Line in Pulsed Electron-Nuclear Double Resonance Spectra

“…The EPR hole broadening associated with the RF-induced inversion of the distant nuclear spins (or any other sources) can be directly observed using a nonselective detection pulse sequence (23,24). The ESE signal formed by this sequence may be considered to consist of two contributions, a narrow intense signal with a positive amplitude due to the electron spins unaffected by the selective preparation pulse and a weak broad negative signal due to the EPR spectrum hole.…”

“…[24] that the hole broadening and the corresponding ESE shape (trace 3 in Fig. 6) should be described by Gaussian functions.…”

“…For the distant matrix nuclei inverted by an RF pulse, the distribution of A is described by Eq. [24]. Taking a convolution of the original EPR hole (Eq.…”

“…To analyze the EPR hole broadening quantitatively, we have used the procedure similar to that employed in (24). We have separated the negative contributions into the ESE signals by subtracting trace 1 from traces 2 and 3 in Fig.…”