Correction: Increasing ion yield circular dichroism in femtosecond photoionisation using optimal control theory

Correction for ‘Increasing ion yield circular dichroism in femtosecond photoionisation using optimal control theory’ by Manel Mondelo-Martell et al., Phys. Chem. Chem. Phys., 2022, 24, 9286–9297, https://doi.org/10.1039/D1CP05239J. The authors have detected two issues in the numerical simulations reported in the originally published version of the article. First, the values of the electric and magnetic transition moments, obtained from quantum chemistry calculations were not sufficiently converged. Second, there was a mistake in the implementation of the rotational averaging in the model. After fixing these errors and choosing an improved optimisation functional, new simulations yield quantitatively different results. However, the physical mechanisms of the optimised pulses identified in the original paper remain valid. Here, the authors summarise the origin of the errors in the original publication and present newly converged energies, permanent and transition moments, as well as corrected figures and conclusions. Specifically, Tables 1 and 2 in the original article have been replaced with the corresponding tables in this correction, and Fig. 2–5 in the original article by Fig. 1–4 in this correction respectively. The authors also introduce and explain the new functional that has been used to optimise the pulse

Pulse length dependence of photoelectron circular dichroism

We investigate photoelectron circular dichroism (PECD) with coherent light sources whose pulse durations range from femtoseconds to nanoseconds. To that end, we employed an optical parametric amplifier, an ultraviolet optical pulse shaper, and a nanosecond dye laser, all centered around a wavelength of 380 nm. A multiphoton ionization experiment on the gas-phase chiral prototype fenchone found that PECD measured via the 3s intermediate resonance is about 15% and robust over five orders of magnitude of the pulse duration. PECD remains robust despite ongoing molecular dynamics such as rotation, vibration, and internal conversion. We used the Lindblad equation to model the molecular dynamics. Under the assumption of a cascading internal conversion, from the 3p to the 3s and further to the ground state, we estimated the lifetimes of the internal conversion processes in the 100 fs regime

Increasing ion yield circular dichroism in femtosecond photoionisation using optimal control theory

We investigate how optimal control theory can be used to improve Circular Dichroism (CD) signals for the A-band of fenchone measured via the photoionization yield upon further excitation. These transitions are electric dipole forbidden to first order, which translates into low population transfer to the excited state but allows for a clearer interplay between electric and magnetic transition dipole moments, which are of the same order of magnitude. Using a model including the electronic ground and excited A state as well as all permanent and transition multipole moments up to the electric quadrupole, we find that the absolute CD signal of randomly oriented molecules can be increased by a factor of 2.5 when using shaped laser pulses, with the anisotropy parameter g increasing from 0.06 to 1. We find that this effect is caused by the interference between the excitation pathways prompted by the different multipole moments of the molecule

Identification of tumor tissue in thin pathological samples via femtosecond laser-induced breakdown spectroscopy and machine learning

Abstract In the treatment of most newly discovered solid cancerous tumors, surgery remains the first treatment option. An important factor in the success of these operations is the precise identification of oncological safety margins to ensure the complete removal of the tumor without affecting much of the neighboring healthy tissue. Here we report on the possibility of applying femtosecond Laser-Induced Breakdown Spectroscopy (LIBS) combined with Machine Learning algorithms as an alternative discrimination technique to differentiate cancerous tissue. The emission spectra following the ablation on thin fixed liver and breast postoperative samples were recorded with high spatial resolution; adjacent stained sections served as a reference for tissue identification by classical pathological analysis. In a proof of principle test performed on liver tissue, Artificial Neural Networks and Random Forest algorithms were able to differentiate both healthy and tumor tissue with a very high Classification Accuracy of around 0.95. The ability to identify unknown tissue was performed on breast samples from different patients, also providing a high level of discrimination. Our results show that LIBS with femtosecond lasers is a technique with potential to be used in clinical applications for rapid identification of tissue type in the intraoperative surgical field

Identification of tumor tissue in thin pathological samples via femtosecond laser-induced breakdown spectroscopy and machine learning

Gefördert durch den Publikationsfonds der Universität Kasse

Self-referencing circular dichroism ion yield measurements for improved statistics using femtosecond laser pulses

Gefördert im Rahmen eines Open-Access-Transformationsvertrags mit dem Verla

Observation of a Long-lived Electronic Coherence Modulated by Vibrational Dynamics in Molecular Nd³+- Complexes at Room Temperature

Gefördert im Rahmen des Projekts DEA