Overcoming the complexity of solid-state sensors through matrix isolation.

• Grant number: 26/03588-9
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2026
• End date: March 31, 2028
• Field of knowledge: Physical Sciences and Mathematics - Physics - Atomic and Molecular Physics
• Principal Investigator: Arnaldo Naves de Brito
• Grantee: Thaïs Jansen Rosset
• Host Institution: Instituto de Física Gleb Wataghin (IFGW). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 24/00998-6 - Center for Research and Innovation on Smart and Quantum Materials (CRISQuaM), AP.CEPID

Abstract

Understanding, on the attosecond-to-low-femtosecond timescale, how electronic charge delocalizes and/or transfers between a small quantum system and its surroundings is essential for designing sensors and functional interfaces based on testable mechanisms rather than trial-and-error. Direct observations of ultrafast charge delocalization/transfer are more commonly associated with comparatively stronger couplings, such as hydrogen-bonded networks or adsorbates strongly hybridized with metals. In contrast, detecting charge transfer in an extremely weakly bound rare-gas matrix-governed primarily by van der Waals interactions-is, in a simplified view, unexpected because the electronic coupling is presumed to be very small.In this Master's project, we will investigate ultrafast charge-transfer/delocalization dynamics in a cryogenic neon matrix with element specificity by combining core-hole clock spectroscopy (CHCS) with high-resolution Resonant Inelastic X-ray Scattering (RIXS) maps and complementary X-ray Absorption Spectroscopy (XAS). In CHCS, the known core-hole lifetime provides an internal time reference, enabling the extraction of a characteristic timescale for electron delocalization/transfer from robust spectral observables.Our team's preliminary results already show unequivocal signatures of charge transfer in a predominantly van der Waals-bound system and, to the best of our knowledge, place this observation among the first direct evidence of ultrafast charge delocalization/transfer under such weak coupling. Moreover, quantitative charge-transfer studies based on electronic spectroscopy remain relatively scarce, and the RIXS + CHCS combination for extracting charge-transfer times is still largely unexplored, making this work a potential starting point for a new experimental direction in charge-transfer dynamics.The project will leverage datasets recorded at the IPÊ beamline (SIRIUS, LNLS/CNPEM). The student will curate, calibrate, and analyze the data, define reproducible metrics (with uncertainty assessment), and extract a characteristic charge-transfer time via CHCS. Deliverables include a reproducible analysis workflow (Igor Pro templates plus a validated Python pipeline), quantitative results for a well-controlled model system, and the Master's thesis. As a complementary CRISQuaM activity, the student will contribute in a clearly bounded manner to instrumentation tasks for a new liquid micro-jet setup, enabling future charge-transfer studies in aqueous environments. (AU)