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Blanchet V, Descamps D, Petit S, Mairesse Y, Pons B, Fabre B. Ultrafast relaxation investigated by photoelectron circular dichroism: an isomeric comparison of camphor and fenchone. Phys Chem Chem Phys 2021; 23:25612-25628. [PMID: 34781331 DOI: 10.1039/d1cp03569j] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We study the isomeric effects using time resolved photoelectron circular dichroism (TR-PECD). Using a (1 + 1') pump-probe ionisation scheme with photoelectrons collected by the velocity map imaging technique, we compare the relaxation dynamics from the 3s-Rydberg state in 1R,4R-(+)-camphor with the one in its chiral isomer, 1R,4S-(-)-fenchone [Comby et al., 2016, JPCL, 7, 4514]. Our measurements revealed a similar lifetime for both isomers. However, the circular dichroism in the photoelectron angular distribution decays exponentially in ∼730 fs from a +9% forward amplitude during the first hundreds of femtoseconds to reach an asymptotic -2% backward amplitude. This time-scale is drastically shorter than in fenchone. Our analysis allows us to evaluate the impact of the anisotropy of excitation; the relaxation dynamics, following photoexcitation by the linearly polarized pump, is then compared to that induced by a circularly polarized pump pulse (CPL). With such a CPL pump, we then retrieve time constants of our chiral observables similar to the ones recorded in fenchone. Quantum and classical simulations are developed and used to decipher the dependence of the PECD on the anisotropy of excitation and the spatial distribution of the 3s-Rydberg electron wavefunction. Our experimental investigations, supported by our simulations, suggest that varying the pump ellipticity enables us to reveal the breakdown of the Franck-Condon approximation.
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Affiliation(s)
- Valérie Blanchet
- Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
| | - Dominique Descamps
- Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
| | - Stéphane Petit
- Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
| | - Yann Mairesse
- Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
| | - Bernard Pons
- Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
| | - Baptiste Fabre
- Université de Bordeaux-CNRS-CEA, CELIA, UMR5107, F33405 Talence, France.
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Martinez P, Blanchet V, Descamps D, Dory JB, Fourment C, Papagiannouli I, Petit S, Raty JY, Noé P, Gaudin J. Sub-Picosecond Non-Equilibrium States in the Amorphous Phase of GeTe Phase-Change Material Thin Films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2102721. [PMID: 34427368 DOI: 10.1002/adma.202102721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 06/01/2021] [Indexed: 06/13/2023]
Abstract
The sub-picosecond response of amorphous germanium telluride thin film to a femtosecond laser excitation is investigated using frequency-domain interferometry and ab initio molecular dynamics. The time-resolved measurement of the surface dynamics reveals a shrinkage of the film with a dielectric properties' response faster than 300 fs. The systematic ab initio molecular dynamics simulations in non-equilibrium conditions allow the atomic configurations to be retrieved for ionic temperature from 300 to 1100 K and width of the electron distribution from 0.001 to 1.0 eV. Local order of the structures is characterized by in-depth analysis of the angle distribution, phonon modes, and pair distribution function, which evidence a transition toward a new amorphous electronic excited state close in bonding/structure to the liquid state. The results shed a new light on the optically highly excited states in chalcogenide materials involved in both important processes: phase-change materials in memory devices and ovonic threshold switching phenomenon induced by a static field.
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Affiliation(s)
- Paloma Martinez
- CELIA, Université Bordeaux, CEA, CNRS, UMR 5107, 351 Cours de la Libération, Talence, F-33405, France
| | - Valérie Blanchet
- CELIA, Université Bordeaux, CEA, CNRS, UMR 5107, 351 Cours de la Libération, Talence, F-33405, France
| | - Dominique Descamps
- CELIA, Université Bordeaux, CEA, CNRS, UMR 5107, 351 Cours de la Libération, Talence, F-33405, France
| | - Jean-Baptiste Dory
- Université Grenoble Alpes, CEA, LETI, 17 rue des Martyrs, Grenoble Cedex 9, F-38000, France
| | - Claude Fourment
- CELIA, Université Bordeaux, CEA, CNRS, UMR 5107, 351 Cours de la Libération, Talence, F-33405, France
- CEA-CESTA, 15 avenue des Sablières, CS 60001, Le Barp CEDEX, F-33116, France
| | - Irène Papagiannouli
- CELIA, Université Bordeaux, CEA, CNRS, UMR 5107, 351 Cours de la Libération, Talence, F-33405, France
| | - Stéphane Petit
- CELIA, Université Bordeaux, CEA, CNRS, UMR 5107, 351 Cours de la Libération, Talence, F-33405, France
| | - Jean-Yves Raty
- Université Grenoble Alpes, CEA, LETI, 17 rue des Martyrs, Grenoble Cedex 9, F-38000, France
- FRS-FNRS and CESAM, University of Liège, Allée du 6 Août 19, Sart-Tilman, 4000, Belgium
| | - Pierre Noé
- Université Grenoble Alpes, CEA, LETI, 17 rue des Martyrs, Grenoble Cedex 9, F-38000, France
| | - Jérôme Gaudin
- CELIA, Université Bordeaux, CEA, CNRS, UMR 5107, 351 Cours de la Libération, Talence, F-33405, France
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