Slow Motion EPR Spectra in Terms of a Generalized Langevin Equation

Length Scales and Dynamics in the Reorientational Relaxation of Tracers in Molecular and Polymeric Glass Formers via Electron Spin Resonance Spectroscopy

“…The analysis of the ESR spectra is well established, and different numerical approaches are usually employed depending on the time scale that characterizes the spin probe dynamics. [55][56][57][58][59][60][61][62] The rotational dynamics is modeled in terms of proper stochastic processes expanding the conditional probability for the molecular orientation P(Ω,t|Ω 0 ,t 0 ) in terms of the Wigner matrices. Different from other spectroscopies probing rotational dynamics, which are sensitive to the fluctuations of Wigner matrices of rank 1 (dielectric spectroscopy, infrared spectroscopy) or 2 (Raman, depolarization of fluorescence, Kerr effect), ESR spectroscopy, in the so-called slow motion regime, depends on the fluctuation of the Wigner matrices of every even rank, having so a greater sensitivity to the detail of the reorientational mechanism.…”

“…On the other hand, it is well-known the great sensitivity of the ESR line shape to the details of the molecular reorientation in the so-called slow motional regime of the paramagnetic system, which usually characterizes reorientational dynamics in the crossover region of glass formers. [55][56][57][58][59][60][61] In this work, ESR experiments on the rotational dynamics of two different paramagnetic probes dissolved in a poly(propylene glycol) matrix are reported. Different dynamical regimes were found with crossover temperatures.…”

Local Reversible Melting in Semicrystalline Poly(dimethylsiloxane): A High-Field Electron Paramagnetic Resonance Study

“…For the calculation of the line shapes we used numerical routines described elsewhere. 73 The same theoretical approach, i.e., the numerical solution of a stochastic Liouville equation, is adopted by alternative computational packages like, e.g., the Matlab-based EasySpin 74 and the NLSL algorithm. 75 Our in-house software and the other two, given the current available computational power and the simple reorientation model of interest here, are equivalent to evaluate the HF-EPR line shapes recorded in the present study.…”

Free radical generation upon plasma treatment of cotton fibers and their initiation efficiency in surface-graft polymerization

“…Eigenvalues and lineshapes can be obtained from this Hamiltonian by numerical simulations [3]. The regime of motion of the system can be defined in terms of the ratio between the molecular time scale and the magnetization time scale [4].…”