ReS 2 is characterized as containing a rich optical and electronic structural diversity due to the stable distorted triclinic 1T crystalline phase owing to the in-plane anisotropic excitons and phonons 2, 3, 4, 5, 6, 7 compared with the isotropic 2H crystal of group-VI TMDs, such as MoS 2 and WSe 2 10, 11, 12, 13, 14, 15, 16, 17, 18, 19. Rhenium disulfide (ReS 2) is a group-VII transition metal dichalcogenide (TMD) material that exhibits considerable potential for photovoltaic applications due to its remarkable optoelectronic properties 1, 2, 3, 4, 5, 6, 7, 8, 9 such as a direct band gap and a large work function 8, 9. This observation was critically examined by considering the allowance of each electronic transition and a small upper band gap (~0.5 eV) using modified DFT calculations. However, the combined usage of a frequency-doubled pump (2.38 eV) with wavelength-variant SHG probes (2.60–2.82 eV) allows us to vividly monitor the variations in TSHG profiles from decay-to-rise to rise-to-decay, which imply the existence of an additional electron absorption state ( s-orbital) at an approximate distance of 5.05 eV from the highest occupied molecular orbital states. The two photon absorptions of 2.38 eV in the excited state that are induced by pumping from 1.57 to 1.72 eV are restricted because these transitions highly correlate with the forbidden d– d intrasubshell orbital transitions. The power and thickness dependencies indicate that the electron–hole recombination is mediated by defects and surfaces. The addition of a pump pulse tuned to the exciton band gap (1.57 eV) creates a decay-to-rise TSHG profile as a function of the probe delay. Up to ~13 nm, a gradual increment is observed, followed by a decrease caused by bulk interferometric light absorption. The second harmonic generation (SHG) of layers with various thicknesses is probed using a 1.19-eV beam. This work shows that serial pain tasks can be used for functional magnetic resonance imaging studies using electrical nerve stimulation as a stimulus, as long as sufficient time is allowed between the two tasks.Here, we investigate the ultrafast carrier dynamics and electronic states of exfoliated ReS 2 films using time-resolved second harmonic generation (TSHG) microscopy and density functional theory (DFT) calculations. Highly significant signal decay was found to exist across each single pain task, but the signal was found to be restored after a 4-min rest period. Significant differences between pain and tingling were found in the ipsilateral cerebellum, contralateral thalamus, secondary somatosensory cortex, primary somatosensory cortex, and anterior cingulate cortex. The time courses of individual voxels were further investigated by analysis of variance with P values of less than 0.05. The average group maps were analyzed by general linear modeling with corrected cluster P values of less than 0.05. Tasks included both tingling and pain induced by transcutaneous electrical stimulation of the median nerve. The characteristics of the brain activation of six subjects were determined using whole brain blood oxygenation level-dependent functional magnetic resonance imaging on a 1.5-T scanner. The signal decay across a task of four repeating pain stimulations and between two serial pain tasks separated by a 4-min interval was examined to determine whether signal attenuation may significantly confound pain investigations. The effect this may have on pain investigations using multiple tasks has not been investigated. Several investigations into brain activation caused by pain have suggested that the multiple painful stimulations used in typical block designs may cause attenuation over time of the signal within activated areas.
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