Adiabatic and fast passage ultra-wideband inversion in pulsed EPR

Doll, Andrin; Pribitzer, Stephan; Tschaggelar, René; Jeschke, Gunnar

doi:10.1016/j.jmr.2013.01.002

Cited by 130 publications

(157 citation statements)

References 41 publications

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“…S3). Moreover, almost all chirp pulses used in this work take into consideration the resonator profile ν 1 ( f ) [26]. Here, we consider idealized resonator profiles parametrized by the quality factor Q L , the resonance frequency f 0 , and the field strength ν 1 .…”

Section: Parameters Of Chirp Pulsesmentioning

confidence: 99%

“…As with any fourpulse DEER experiment with chirp pulses, the approach has a shortcoming at short distances due to the extended pulse duration of the pump pulse. Previously, we could faithfully obtain a distance distribution with a mean distance of 2.5 nm with a 64 ns pulse on a different system [26]. Five-pulse DEER techniques are considered to be free of this limitation [27].…”

Section: Consecutive Chirp Pulsesmentioning

confidence: 99%

“…In this work, we investigate how Gd-Gd DEER experiments can be improved with chirp pump pulses synthesized by an arbitrary waveform generator (AWG). A key advantage of arbitrarily shaped pulses is the improved excitation bandwidth, as demonstrated in a number of recent studies [25][26][27][28][29][30][31][32]. For chirp pulses, pulse performance can be quantified by the critical adiabaticity factor Q crit using the Landau-Zener equation [31].…”

Section: Introductionmentioning

confidence: 99%

“…For chirp pulses, pulse performance can be quantified by the critical adiabaticity factor Q crit using the Landau-Zener equation [31]. Moreover, limitations in excitation bandwidth imposed by the resonator can be compensated by adaptation of the frequency sweep of the chirp pulse to the resonator profile, which establishes ultra-wideband (UWB) EPR [26,28].…”

Section: Introductionmentioning

confidence: 99%

“…In principle, the DEER pump pulse should have a large adiabaticity factor for efficient inversion, which also requires long and intense pulses. However, experiments on S = 1/2 spins have shown that interference prohibits the use of long chirp pulses in four-pulse DEER [26,27]. The key subject of this work is to identify and eventually alleviate additional limitations specific to the Gd(III) high-spin state with respect to chirp pump pulses.…”

Section: Introductionmentioning

confidence: 99%

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Gd(III)–Gd(III) distance measurements with chirp pump pulses

Doll

Wili

et al. 2015

Journal of Magnetic Resonance

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The broad EPR spectrum of Gd(III) spin labels restricts the dipolar modulation depth in distance measurements between Gd(III) pairs to a few percent. To overcome this limitation, frequency-swept chirp pulses are utilized as pump pulses in the DEER experiment. Using a model system with 3.4 nm Gd-Gd distance, application of one single chirp pump pulse at Q-band frequencies leads to modulation depths beyond 10%. However, the larger modulation depth is counteracted by a reduction of the absolute echo intensity due to the pump pulse. As supported by spin dynamics simulations, this effect is primarily driven by signal loss to double-quantum coherence and specific to the Gd(III) high spin state of S = 7/2. In order to balance modulation depth and echo intensity for optimum sensitivity, a simple experimental procedure is proposed. An additional improvement by 25% in DEER sensitivity is achieved with two consecutive chirp pump pulses. These pulses pump the Gd(III) spectrum symmetrically around the observation position, therefore mutually compensating for dynamical Bloch-Siegert phase shifts at the observer spins. The improved sensitivity of the DEER data with modulation depths on the order of 20% is due to mitigation of the echo reduction effects by the consecutive pump pulses. In particular, the second pump pulse does not lead to additional signal loss if perfect inversion is assumed. Moreover, the compensation of the dynamical Bloch-Siegert phase prevents signal loss due to spatial dependence of the dynamical phase, which is caused by inhomogeneities in the driving field. The new methodology is combined with pre-polarization techniques to measure long distances up to 8.6 nm, where signal intensity and modulation depth become attenuated by long dipolar evolution windows. In addition, the influence of the zero-field splitting parameters on the echo intensity is studied with simulations. Herein, larger sensitivity is anticipated for Gd(III) complexes with zero-field splitting that is smaller than for the employed Gd-PyMTA complex.

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Section: Parameters Of Chirp Pulsesmentioning

confidence: 99%

Section: Consecutive Chirp Pulsesmentioning

confidence: 99%