National Aeronautics and Space Administration's Magnetosphere Multiscale mission reveals that agyrotropic electrons and intense waves are prevalently present in the electron diffusion region. Prompted by two distinct Magnetosphere Multiscale observations, this letter investigates by theoretical means and the properties of agyrotropic electron beam‐plasma instability and explains the origin of different structures in the wave spectra. The difference is owing to the fact that in one instance, a continuous beam mode is excited, while in the other, discrete Bernstein modes are excited, and the excitation of one mode versus the other depends on physical input parameters, which are consistent with observations. Analyses of dispersion relations show that the growing mode becomes discrete when the maximum growth rate is lower than the electron cyclotron frequency. Making use of particle‐in‐cell simulations, we found that the broadening angle
Relations between absorption, emission, and excited state chemical potentials from nanocrystal 2D spectra
For quantum-confined nanomaterials, size dispersion causes a static broadening of spectra that has been difficult to measure and invalidates all-optical methods for determining the maximum photovoltage that an excited state can generate. Using femtosecond two-dimensional (2D) spectroscopy to separate size dispersion broadening of absorption and emission spectra allows a test of single-molecule generalized Einstein relations between such spectra for colloidal PbS quantum dots. We show that 2D spectra and these relations determine the thermodynamic standard chemical potential difference between the lowest excited and ground electronic states, which gives the maximum photovoltage. Further, we find that the static line broadening from many slightly different quantum dot structures allows single-molecule generalized Einstein relations to determine the average single-molecule linewidth from Stokes’ frequency shift between ensemble absorption and emission spectra.
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- Award ID(s):
- 1800523
- NSF-PAR ID:
- 10292106
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 7
- Issue:
- 22
- ISSN:
- 2375-2548
- Page Range / eLocation ID:
- eabf4741
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract in the gyroangle space is also an important factor controlling the growth rate. Ramifications of the present finding are also discussed. -
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/sciadv.abf4741
