Spectroscopic capabilities of the time-resolved magnetic field effect technique as illustrated in the study of hexamethylethane radical cation in liquid hexane

Bagryansky, V. A.; Borovkov, V. I.; Molin, Yuri N.

doi:10.1039/b311315a

Cited by 22 publications

(44 citation statements)

References 18 publications

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“…RYDMR signals can be observed in two different ways. In the first observation mode, the concentration of the RP recombination product is monitored in real time [11,[15][16][17]. In turn, the rate of the product formation is proportional to the fraction of RPs in the singlet state, equal to ρ SS (t).…”

Section: Rydmr Observablementioning

confidence: 99%

“…Thus, in such an experiment it becomes possible to measure the time dependence of ρ SS (t). Experiments of this kind are done, for instance, for detecting radical ion pairs in non-polar solutions by monitoring the luminescence of the singlet-state recombination product [15][16][17]. When the luminescence time is short, the luminescence kinetics gives the ρ SS (t) time dependence.…”

Section: Rydmr Observablementioning

confidence: 99%

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Theoretical Description of Pulsed RYDMR: Refocusing Zero-Quantum and Single Quantum Coherences

Nasibulov

Behrends

Кулик

et al. 2016

Zeitschrift Für Physikalische Chemie

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A theoretical description of pulsed reaction yield detected magnetic resonance (RYDMR) is proposed. In RYDMR, magnetic resonance spectra of radical pairs (RPs) are indirectly detected by monitoring their recombination yield. Such a detection method is significantly more sensitive than conventional electron paramagnetic resonance (EPR), but design of appropriate pulse sequences for RYDMR requires additional effort because of a different observable. In this work various schemes for generating spin-echo like signals and detecting them by RYDMR are treated. Specifically, we consider refocusing of zero-quantum coherences (ZQCs) and single-quantum coherences (SQCs) by selective as well as by non-selective pulses and formulate a general analytical approach to pulsed RYDMR, which makes an efficient use of the product operator formalism. We anticipate that these results are of importance for RYDMR studies of elusive paramagnetic particles, notably, in organic semiconductors.

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Section: Rydmr Observablementioning

confidence: 99%

Section: Rydmr Observablementioning

confidence: 99%

Theoretical Description of Pulsed RYDMR: Refocusing Zero-Quantum and Single Quantum Coherences

Nasibulov

Behrends

Кулик

et al. 2016

Zeitschrift Für Physikalische Chemie

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“…For this reason Reaction Yield Detected Magnetic Resonance (RYDMR) techniques have been developed. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] They enable detection of magnetic resonance spectra indirectly by choosing a different observable, which can be optical absorption or luminescence of the product of RP recombination (optically detected EPR, or OD EPR) or photo-current (electrically detected magnetic resonance, or EDMR).…”

Section: Introductionmentioning

confidence: 99%

Theory of pulsed reaction yield detected magnetic resonance

Nasibulov

Кулик

Kaptein

et al. 2012

Phys. Chem. Chem. Phys.

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We propose pulse sequences for Reaction Yield Detected Magnetic Resonance (RYDMR), which are based on refocusing the zero-quantum coherences in radical pairs by non-selective microwave pulses and using the population of a radical pair singlet spin state as an observable. The new experiments are analogues of existing EPR experiments such as the primary echo, Carr-Purcell, ESEEM, stimulated echo and Mims ENDOR. All pulse sequences are supported by analytical results and numerical calculations. The pulse sequences can be used for more efficient and highly detailed characterization of intermediates of chemical reactions and charge carriers in organic semiconductors.

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“…Therefore, in simulation of TR MFE curves, the singlet state population ρ ss (t) in strong and zero fields was calculated numerically. The spin relaxation times of the radical ions in the pair were considered in the framework of approximations described elsewhere [3,5].Studies of radical anions by the TR MFE method were carried out in 1-10 mM liquid solutions of TFB and PFA in 2,2,4 trimethylpentane (isooctane). In isooctane, the mobility of excess electrons is very high, and radical anions of electron acceptors form in the subnanosecond time domain.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Time-resolved magnetic field effect as a method of studying radical pairs with rapid evolution of spin state

et al. 2015

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103As a rule, organic radical ions in solutions have rather short lifetimes, which makes them unsuitable for study by ESR, and at lifetimes shorter than 10 ns, even by a more sensitive method of optically detected ESR (OD ESR) of spin correlated radical ion pairs [1,2]. At the same time, the method of time resolved mag netic field effect (TR MFE) in recombination fluores cence of such pairs [2, 3] enables the detection of even shorter lived particles. This possibility is determined, first of all, by the time resolution of a setup, which we have managed to improve to ≈1 ns. An additional nec essary condition for identification of such short lived radicals is the existence of hyperfine coupling (HFC) constants in them sufficiently large (≈10 mT) to induce singlet-triplet transitions in the nanosecond time range. It is worth noting that the class of com pounds of interest includes only those with rather short fluorescence times.In this work, the potentialities of the TR MFE method have been demonstrated by the examples of radical anions of two fluoro substituted aromatic compounds-1,2,3,5 tetrafluorobenzene (TFB) and pentafluoroaniline (PFA)-generated by X ray irradi ation of solutions. This method is based on analysis of specific features of the ratio between the kinetic curves of recombination fluorescence in a magnetic field (I B (t) and in the absence of a field (I 0 (t)). In low polar ity solutions, the fluorescence intensity decay caused by recombination of radical ion pairs, in the limit of infinitely short fluorescence time and narrow instru mental function, is given bywhere F(t) is the pair recombination rate, θ is the frac tion of pairs generated in the singlet correlated state, and ρ ss (t) is the population of the singlet stage of such pairs [3]. In this approximation, the ratio(2) referred to as time resolved magnetic field effect, is independent of recombination kinetics F(t). However, at sufficiently high frequencies of ρ ss (t) oscillations caused by large HFC constants, the fluorescence kinetics must be described, not by Eq.(1), but by its integral convolution with the fluorescence probability of excited molecules, which changes exponentially with time, and the Gaussian instrumental function (see, e.g., [4]). Radical ions studied in this work have more than two different HFC constants. Therefore, in simulation of TR MFE curves, the singlet state population ρ ss (t) in strong and zero fields was calculated numerically. The spin relaxation times of the radical ions in the pair were considered in the framework of approximations described elsewhere [3,5].Studies of radical anions by the TR MFE method were carried out in 1-10 mM liquid solutions of TFB and PFA in 2,2,4 trimethylpentane (isooctane). In isooctane, the mobility of excess electrons is very high, and radical anions of electron acceptors form in the subnanosecond time domain. To reduce the contribu tion of the isooctane radical cation (the ESR spectrum width, ≈2 mT) to the spin evolution of the radical pair, a positive charge acceptor-hexameth...

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Spectroscopic capabilities of the time-resolved magnetic field effect technique as illustrated in the study of hexamethylethane radical cation in liquid hexane

Cited by 22 publications

References 18 publications

Theoretical Description of Pulsed RYDMR: Refocusing Zero-Quantum and Single Quantum Coherences

Theoretical Description of Pulsed RYDMR: Refocusing Zero-Quantum and Single Quantum Coherences

Theory of pulsed reaction yield detected magnetic resonance

Time-resolved magnetic field effect as a method of studying radical pairs with rapid evolution of spin state

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