PyAbel (v0.7): A Python Package for Abel Transforms

<p>PyAbel is an open-source Python package for performing Abel transforms (both forward and inverse). The forward Abel transform is used to transform a slice of a 3D object into a 2D projection of the object. The inverse Abel transform accomplished the opposite, taking a 2D projection of the object and providing a slice of the 3D object. To use the Abel transform, the object must have cylindrical symmetry, and that axis of cylindrical symmetry must lie in the plane of the 2D image.</p> <p>Inverse Abel transforms are commonly used in processing images derived from photoelectron/photoion spectroscopy experiments, ultracold atom (Bose-Einstein condensates) experiments, and in the analysis of flames and plasma plumes. Basically, these are all cases where projections of cylindrically symmetric structures are recorded. </p> <p>PyAbel incorporates several of the most popular Abel Transform algorithms, including:</p> <p>    1. The Gaussian basis set expansion of Dribinski and co-workers (BASEX)</p> <p>    2.  The recursive method of Hansen and Law.</p> <p>    3. Direct numerical integration of the analytical Abel transform equations.</p> <p>    4. The "three point" method of Dasch and co-workers.</p> <p>PyAbel achieves highly efficient implementations of these Abel transform methods in an easy-to-use Python package. PyAbel also includes a set of tools for centering, symmetrizing, and integrating images.</p> <p>PyAbel is available under the MIT license.</p

Solvents Effects on Charge Transfer from Quantum Dots

To predict and understand the performance of nanodevices in different environments, the influence of the solvent must be explicitly understood. In this Communication, this important but largely unexplored question is addressed through a comparison of quantum dot charge transfer processes occurring in both liquid phase and in vacuum. By comparing solution phase transient absorption spectroscopy and gas-phase photoelectron spectroscopy, we show that hexane, a common nonpolar solvent for quantum dots, has negligible influence on charge transfer dynamics. Our experimental results, supported by insights from theory, indicate that the reorganization energy of nonpolar solvents plays a minimal role in the energy landscape of charge transfer in quantum dot devices. Thus, this study demonstrates that measurements conducted in nonpolar solvents can indeed provide insight into nanodevice performance in a wide variety of environments

Materials Properties and Solvated Electron Dynamics of Isolated Nanoparticles and Nanodroplets Probed with Ultrafast Extreme Ultraviolet Beams

We present ultrafast photoemission measurements of isolated nanoparticles in vacuum using extreme ultraviolet (EUV) light produced through high harmonic generation. Surface-selective static EUV photoemission measurements were performed on nanoparticles with a wide array of compositions, ranging from ionic crystals to nanodroplets of organic material. We find that the total photoelectron yield varies greatly with nanoparticle composition and provides insight into material properties such as the electron mean free path and effective mass. Additionally, we conduct time-resolved photoelectron yield measurements of isolated oleylamine nanodroplets, observing that EUV photons can create solvated electrons in liquid nanodroplets. Using photoemission from a time-delayed 790 nm pulse, we observe that a solvated electron is produced in an excited state and subsequently relaxes to its ground state with a lifetime of 151 ± 31 fs. This work demonstrates that femotosecond EUV photoemission is a versatile surface-sensitive probe of the properties and ultrafast dynamics of isolated nanoparticles

Mapping Nanoscale Absorption of Femtosecond Laser Pulses Using Plasma Explosion Imaging

We make direct observations of localized light absorption in a single nanostructure irradiated by a strong femtosecond laser field, by developing and applying a technique that we refer to as plasma explosion imaging. By imaging the photoion momentum distribution resulting from plasma formation in a laser-irradiated nanostructure, we map the spatial location of the highly localized plasma and thereby image the nanoscale light absorption. Our method probes individual, isolated nanoparticles in vacuum, which allows us to observe how small variations in the composition, shape, and orientation of the nanostructures lead to vastly different light absorption. Here, we study four different nanoparticle samples with overall dimensions of ∼100 nm and find that each sample exhibits distinct light absorption mechanisms despite their similar size. Specifically, we observe subwavelength focusing in single NaCl crystals, symmetric absorption in TiO₂ aggregates, surface enhancement in dielectric particles containing a single gold nanoparticle, and interparticle hot spots in dielectric particles containing multiple smaller gold nanoparticles. These observations demonstrate how plasma explosion imaging directly reveals the diverse ways in which nanoparticles respond to strong laser fields, a process that is notoriously challenging to model because of the rapid evolution of materials properties that takes place on the femtosecond time scale as a solid nanostructure is transformed into a dense plasma