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2. Electrochemical Doping in Ordered and Disordered Domains of Conjugated Polymers

Author

Cavassin, Priscila, Holzer, Isabelle, Tsokkou, Demetra, Bardagot, Oliver, Réhault, Julien, and Banerji, Natalie

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Conjugated polymers are increasingly used as organic mixed ionic-electronic conductors in electrochemical devices for neuromorphic computing, bioelectronics and energy harvesting. The design of efficient applications relies on high electrochemical doping levels, high electronic conductivity, fast doping/dedoping kinetics and high ionic uptake. In this work, we establish structure-property relations and demonstrate how these parameters can be modulated by the co-existence of order and disorder. We use in-situ time-resolved spectroelectrochemistry, resonant Raman and terahertz conductivity measurements to investigate the electrochemical doping in the different morphological domains of poly(3-hexylthiophene). Our main finding is that bipolarons are found preferentially in disordered polymer regions, where they are formed faster and are thermodynamically more favoured. On the other hand, polarons show a preference for ordered domains, leading to drastically different bipolaron/polaron ratios and doping/dedoping dynamics in the distinct regions. We evidence a significant enhancement of the electronic conductivity when bipolarons start being formed in the disordered regions, while the presence of bipolarons in the ordered regions is detrimental for transport. Our study provides significant advances in the understanding of the impact of morphology on the electrochemical doping of conjugated polymers and the induced increase in conductivity.

Published
2022

4. Watching the coherent birth of polaron pairs in conjugated polymers

Author

De Sio, Antonietta, Troiani, Filippo, Maiuri, Margherita, Réhault, Julien, Sommer, Ephraim, Lim, James, Huelga, Susana F., Plenio, Martin B., Rozzi, Carlo Andrea, Cerullo, Giulio, Molinari, Elisa, and Lienau, Christoph

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Soft Condensed Matter, Physics - Chemical Physics, Quantum Physics
Abstract

Organic semiconductors have the remarkable property that their optical excitation not only generates charge-neutral electron-hole pairs (excitons) but also charge-separated polaron pairs with high yield. The microscopic mechanisms underlying this charge separation have been debated for many years. Here we use ultrafast two-dimensional electronic spectroscopy to study the dynamics of polaron pair formation in a prototypical polymer thin film on a sub-20-fs time scale. We observe multi-period peak oscillations persisting for up to about 1 ps as distinct signatures of vibronic quantum coherence at room temperature. The measured two-dimensional spectra show pronounced peak splittings revealing that the elementary optical excitations of this polymer are hybridized exciton-polaron-pairs, strongly coupled to a dominant underdamped vibrational mode. Coherent vibronic coupling induces ultrafast polaron pair formation, accelerates the charge separation dynamics and makes it insensitive to disorder. These findings open up new perspectives for tailoring light-to-current conversion in organic materials.

Published
2016
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5. Noncollinear, inelastic four-wave mixing in the extreme ultraviolet

Author

Mincigrucci, Riccardo, primary, Cannizzo, Andrea, additional, capotondi, flavio, additional, Cinquegrana, Paolo, additional, Cucini, Riccardo, additional, Dallari, Francesco, additional, Danailov, M, additional, de Ninno, Giovanni, additional, Di Mitri, Simone, additional, Feurer, Thomas, additional, Foglia, Laura, additional, Frey, Hans-Martin, additional, Manfredda, Michele, additional, Maznev, Alexei, additional, Monaco, Giulio, additional, Naumenko, Denys, additional, Nikolov, Ivaylo, additional, Ollmann, Zoltán, additional, Paltanin, Ettore, additional, Pamfilidis, Georgios, additional, Pedersoli, Emanuele, additional, Principi, Emiliano, additional, Réhault, Julien, additional, Simoncig, Alberto, additional, Svetina, Cristian, additional, Knopp, Gregor, additional, Masciovecchio, Claudio, additional, and Bencivenga, Filippo, additional

Published
2023
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8. A Quasi‐2D Polypyrrole Film with Band‐Like Transport Behavior And High Charge Carrier Mobility

Author

Liu, Kejun, primary, Réhault, Julien, additional, Liang, Baokun, additional, Hambsch, Mike, additional, Zhang, Yingying, additional, Seçkin, Sezer, additional, Zhou, Yunxia, additional, Shivhare, Rishi, additional, Zhang, Peng, additional, Polozij, Miroslav, additional, König, Tobias A. F., additional, Qi, Haoyuan, additional, Zhou, Shengqiang, additional, Fery, Andreas, additional, Mannsfeld, Stefan C. B., additional, Kaiser, Ute, additional, Heine, Thomas, additional, Banerji, Natalie, additional, Dong, Renhao, additional, and Feng, Xinliang, additional

Published
2023
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9. Sub-picosecond charge-transfer at near-zero driving force in polymer:non-fullerene acceptor blends and bilayers

Author

Zhong, Yufei, Causa’, Martina, Moore, Gareth John, Krauspe, Philipp, Xiao, Bo, Günther, Florian, Kublitski, Jonas, Shivhare, Rishi, Benduhn, Johannes, BarOr, Eyal, Mukherjee, Subhrangsu, Yallum, Kaila M., Réhault, Julien, Mannsfeld, Stefan C. B., Neher, Dieter, Richter, Lee J., DeLongchamp, Dean M., Ortmann, Frank, Vandewal, Koen, Zhou, Erjun, and Banerji, Natalie

Published
2020
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10. Electrochemical Doping in Ordered and Disordered Domains of Organic Mixed Ionic-Electronic Conductors

Author

Cavassin, Priscila, Holzer, Isabelle, Tsokkou, Demetra, Bardagot, Olivier, Réhault, Julien, and Banerji, Natalie

Subjects
Mechanics of Materials, Mechanical Engineering, 540 Chemistry, 570 Life sciences, biology, General Materials Science
Abstract

Conjugated polymers are increasingly used as organic mixed ionic-electronic conductors in electrochemical applications for neuromorphic computing, bioelectronics and energy harvesting. The design of efficient electrochemical devices relies on large modulations of the polymer conductivity, fast doping/dedoping kinetics, and high ionic uptake. In this work, structure-property relations are established and control of these parameters by the co-existence of order and disorder in the phase morphology is demonstrated. Using in-situ time-resolved spectroelectrochemistry, resonant Raman and terahertz conductivity measurements, the electrochemical doping in the different morphological domains of poly(3-hexylthiophene) is investigated. The main finding is that bipolarons are found preferentially in disordered polymer regions, where they are formed faster and are thermodynamically more favoured. On the other hand, polarons show a preference for ordered domains, leading to drastically different bipolaron/polaron ratios and doping/dedoping dynamics in the distinct regions. A significant enhancement of the electronic conductivity is evident when bipolarons start forming in the disordered regions, while the presence of bipolarons in the ordered regions is detrimental for transport. This study provides significant advances in the understanding of the impact of morphology on the electrochemical doping of conjugated polymers and the induced increase in conductivity. This article is protected by copyright. All rights reserved.

Published
2023
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11. A Quasi-2D Polypyrrole Film with Band-Like Transport Behavior And High Charge Carrier Mobility

Author

Liu, Kejun, Réhault, Julien, Liang, Baokun, Hambsch, Mike, Zhang, Yingying, Seçkin, Sezer, Zhou, Yunxia, Shivhare, Rishi, Zhang, Peng, Polozij, Miroslav, König, Tobias A F, Qi, Haoyuan, Zhou, Shengqiang, Fery, Andreas, Mannsfeld, Stefan C B, Kaiser, Ute, Heine, Thomas, Banerji, Natalie, Dong, Renhao, and Feng, Xinliang

Subjects
540 Chemistry, 570 Life sciences, biology, 000 Computer science, knowledge & systems
Abstract

Quasi-two-dimensional conjugated polymers (q2DCPs) are polymers that consist of linear conjugated polymer chains assembled through non-covalent interactions to form a layered structure. In this work, w e report the synthesis of a novel crystalline q2D polypyrrole (q2DPPy) film at an air/H2 SO4 (95%) interface. The unique interfacial environment facilitated chain extension, prevented disorder, and resulted in a crystalline, layered assembly of protonated quinoidal chains with a fully extended conformation in its crystalline domains. This unique structure features highly delocalized π-electron systems within the extended chains, which is responsible for the low effective mass and narrow electronic bandgap. Thus w e investigated the temperature-dependent charge transport properties of q2DPPy using the van der Pauw (vdP) method and terahertz time-domain spectroscopy (THz-TDS). The vdP method revealed that the q2DPPy film exhibited a semiconducting behavior with a thermally activated hopping mechanism in long-range transport between the electrodes. Conversely, THz-TDS revealed a band-like transport, indicating intrinsic charge transport up to a record short-range high THz mobility of ∼107.1 cm2 V-1 s-1 . This article is protected by copyright. All rights reserved.

Published
2023
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14. A new single shot THz detection strategy with electro-optic sampling

Author

Krauspe, Philipp, Banerji, Natalie, and Réhault, Julien

Subjects
540 Chemistry, 570 Life sciences, biology
Abstract

We present a new technique for single shot Terahertz detection in electro-optics sampling (EOS) with a narrowband probe pulse shaped using a Fabry-Pérot etalon. The technique allows tdetection in the frequency domain using a high-resolution CCD spectrometer. The technique is simple and sensitive. It has a high time resolution and can be simply implemented in a standard EOS scanning experiment.

Published
2022
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19. Matlab Code for reconstruction of SFG spectra

Author

Schweizer, Tobias, Nicolau, Bruno, Cavassin, Priscila, Feurer, Thomas, Banerji, Natalie, and Réhault, Julien

Subjects
540 Chemistry
Abstract

We demonstrate that time-domain ptychography, when applied to a set of broadband vibrational sum frequency spectra, reconstructs amplitude and phase of the vibrational free induction decay from an interfacial sample with a resolution that is independent of the up-converting pulse bandwidth and spectrometer resolution. These important improvements require no modifications to most standard homodyne setups and the method is applicable to other coherent homodyne spectroscopies like coherent anti-Stokes Raman spectroscopy or transient grating spectroscopy.

Published
2020
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20. Data related to 'Sub-picosecond charge-transfer at near-zero driving force in polymer:non-fullerene acceptor blends and bilayers', Nature Communications (2020), DOI 10.1038/s41467-020-14549-w

Author

Zhong, Yufei, Causa', Martina, Moore, Gareth John, Krauspe, Philipp Jonathan, Xiao, Bo, Günther, Florian, Kublitski, Jonas, Shivhare, Rishi Ramdas, Benduhn, Johannes, BarOr, Eyal, Mukherjee, Subhrangsu, Yallum, Kaila Morgan, Réhault, Julien Emile, Mannsfeld, Stefan C. B., Neher, Dieter, Richter, Lee J., DeLongchamp, Dean M., Ortmann, Frank, Vandewal, Koen, Zhou, Erjun, and Banerji, Natalie

Subjects
540 Chemistry
Published
2020
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21. Experimental SFG spectra

Author

Schweizer, Tobias, Nicolau, Bruno, Cavassin, Priscila, Feurer, Thomas, Banerji, Natalie, and Réhault, Julien

Subjects
540 Chemistry, 570 Life sciences, biology
Abstract

We demonstrate that time-domain ptychography, when applied to a set of broadband vibrational sum frequency spectra, reconstructs amplitude and phase of the vibrational free induction decay from an interfacial sample with a resolution that is independent of the up-converting pulse bandwidth and spectrometer resolution. These important improvements require no modifications to most standard homodyne setups and the method is applicable to other coherent homodyne spectroscopies like coherent anti-Stokes Raman spectroscopy or transient grating spectroscopy.

Published
2020
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23. What Drives the Kinetics and Doping Level in the Electrochemical Reactions of PEDOT:PSS?

Author

Rebetez, Gonzague, Bardagot, Olivier, Affolter, Joël, Réhault, Julien, and Banerji, Natalie

Subjects
ENTROPY, ELECTROLYTES, EQUILIBRIUM, VOLTAGE, OXIDATION-reduction reaction
Abstract

The electrochemical dedoping and redoping processes of a thin poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film immersed in an electrolyte are studied at different temperatures with time‐resolved spectroelectrochemistry in the visible and near‐infrared range. The spectral signatures of neutral, polaronic, and bipolaronic states of PEDOT are resolved using multivariate curve resolution analysis. Kinetic modeling of their dynamics reveals that both the dedoping and redoping are sequential processes and occur within a few hundred milliseconds in the system. Evaluation of the temperature‐dependence with the Van't Hoff, Arrhenius, and Eyring formalisms highlights the role of entropy in both the establishment of the redox equilibrium at a given voltage bias and the reaction rates. This study provides a significant understanding of the fundamental mechanisms determining the level and rate of the electrochemical processes in PEDOT:PSS and will help tailor the design of faster and more efficient bioelectronic devices based on mixed ionic–electronic conductors. [ABSTRACT FROM AUTHOR]

Published
2022
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24. Ultra-broadband 2D electronic spectroscopy of carotenoid-bacteriochlorophyll interactions in the LH1 complex of a purple bacterium.

Author

Maiuri, Margherita, Réhault, Julien, Carey, Anne-Marie, Hacking, Kirsty, Garavelli, Marco, Lüer, Larry, Polli, Dario, Cogdell, Richard J., and Cerullo, Giulio

Subjects
*ELECTRONIC spectra, *CAROTENOIDS, *BACTERIOCHLOROPHYLLS, *EXCITATION energy (In situ microanalysis), *ENERGY transfer
Abstract

We investigate the excitation energy transfer (EET) pathways in the photosynthetic light harvesting 1 (LH1) complex of purple bacterium Rhodospirillum rubrum with ultra-broadband two-dimensional electronic spectroscopy (2DES). We employ a 2DES apparatus in the partially collinear geometry, using a passive birefringent interferometer to generate the phase-locked pump pulse pair. This scheme easily lends itself to two-color operation, by coupling a sub-10 fs visible pulse with a sub-15-fs near-infrared pulse. This unique pulse combination allows us to simultaneously track with extremely high temporal resolution both the dynamics of the photoexcited carotenoid spirilloxanthin (Spx) in the visible range and the EET between the Spx and the B890 bacterio-chlorophyll (BChl), whose Qx and Qy transitions peak at 585 and 881 nm, respectively, in the near-infrared. Global analysis of the one-color and two-color 2DES maps unravels different relaxation mechanisms in the LH1 complex: (i) the initial events of the internal conversion process within the Spx, (ii) the parallel EET from the first bright state S2 of the Spx towards the Qx state of the B890, and (iii) the internal conversion from Qx to Qy within the B890. [ABSTRACT FROM AUTHOR]

Published
2015
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25. Data related to manuscript [‘Effective detection of weak terahertz pulses in electro-optic sampling at kilohertz repetition rate, Journal of the Optical Society of America B (2019), https://doi.org/10.1364/JOSAB.37.000127]

Author

Krauspe, Philipp Jonathan, Banerji, Natalie, and Réhault, Julien Emile

Subjects
530 Physics, 540 Chemistry, 570 Life sciences, biology
Abstract

The standard terahertz (THz) detection mechanism known as electro-optic sampling can be improved in sensitivity by biasing the polarization of the sampling field. In this work, we show theoretically and experimentally how weak signals can be amplified without inducing distortions. Our study identifies the influence of THz field strength, the polarization quality, and biasing amplitude on signal amplification and distortion. Here we present a distortion- free amplification of a factor of 28 while at the same time reducing the measurement time significantly.

Published
2019
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27. Ultrafast Carotenoid to Retinal Energy Transfer in Xanthorhodopsin Revealed by the Combination of Transient Absorption and Two‐Dimensional Electronic Spectroscopy

Author

Segatta, Francesco, primary, Gdor, Itay, additional, Réhault, Julien, additional, Taioli, Simone, additional, Friedman, Noga, additional, Sheves, Mordechai, additional, Rivalta, Ivan, additional, Ruhman, Sanford, additional, Cerullo, Giulio, additional, and Garavelli, Marco, additional

Published
2018
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29. Linear dichroism amplification: Adapting a long-known technique for ultrasensitive femtosecond IR spectroscopy.

Author

Réhault, Julien, Zanirato, Vinicio, Olivucci, Massimo, and Helbing, Jan

Subjects
*LINEAR dichroism, *INFRARED spectroscopy, *OPTICAL polarization, *LASER spectroscopy, *SCHIFF bases, *POLARIZERS (Light), *PHOTOCHEMISTRY, *LIGHT modulators
Abstract

We demonstrate strong amplification of polarization-sensitive transient IR signals using a pseudo-null crossed polarizer technique first proposed by Keston and Lospalluto [Fed. Proc. 10, 207 (1951)] and applied for nanosecond flash photolysis in the visible by Che et al. [Chem. Phys. Lett. 224, 145 (1994)]. We adapted the technique to ultrafast pulsed laser spectroscopy in the infrared using photoelastic modulators, which allow us to measure amplified linear dichroism at kilohertz repetition rates. The method was applied to a photoswitch of the N-alkylated Schiff base family in order to demonstrate its potential of strongly enhancing sensitivity and signal to noise in ultrafast transient IR experiments, to simplify spectra and to determine intramolecular transition dipole orientations. [ABSTRACT FROM AUTHOR]

Published
2011
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30. Time-domain measurement of optical activity by an ultrastable common-path interferometer

Author

Preda, Fabrizio; https://orcid.org/0000-0002-1055-8900, Perri, Antonio; https://orcid.org/0000-0002-1283-8535, Réhault, Julien; https://orcid.org/0000-0002-6565-3016, Dutta, Biplab, Helbing, Jan; https://orcid.org/0000-0003-3911-8519, Cerullo, Giulio; https://orcid.org/0000-0002-9534-2702, Polli, Dario; https://orcid.org/0000-0002-6960-5708, Preda, Fabrizio; https://orcid.org/0000-0002-1055-8900, Perri, Antonio; https://orcid.org/0000-0002-1283-8535, Réhault, Julien; https://orcid.org/0000-0002-6565-3016, Dutta, Biplab, Helbing, Jan; https://orcid.org/0000-0003-3911-8519, Cerullo, Giulio; https://orcid.org/0000-0002-9534-2702, and Polli, Dario; https://orcid.org/0000-0002-6960-5708

Abstract

We introduce a novel configuration for the broadband measurement of the optical activity of molecules, combining time-domain detection with heterodyne amplification. A birefringent common-path polarization-division interferometer creates two phase-locked replicas of the input light with orthogonal polarization. The more intense replica interacts with the sample, producing a chiral free-induction decay field, which interferes with the other replica, acting as a time-delayed phase-coherent local oscillator. By recording the delay-dependent interferogram, we obtain by a Fourier transform both the circular dichroism and circular birefringence spectra. Our compact, low-cost setup accepts ultrashort light pulses, making it suitable for measurement of transient optical activity.

Published
2018

31. SwissFEL: The Swiss X-ray Free Electron Laser

Author

Milne, Christopher, primary, Schietinger, Thomas, additional, Aiba, Masamitsu, additional, Alarcon, Arturo, additional, Alex, Jürgen, additional, Anghel, Alexander, additional, Arsov, Vladimir, additional, Beard, Carl, additional, Beaud, Paul, additional, Bettoni, Simona, additional, Bopp, Markus, additional, Brands, Helge, additional, Brönnimann, Manuel, additional, Brunnenkant, Ingo, additional, Calvi, Marco, additional, Citterio, Alessandro, additional, Craievich, Paolo, additional, Csatari Divall, Marta, additional, Dällenbach, Mark, additional, D’Amico, Michael, additional, Dax, Andreas, additional, Deng, Yunpei, additional, Dietrich, Alexander, additional, Dinapoli, Roberto, additional, Divall, Edwin, additional, Dordevic, Sladana, additional, Ebner, Simon, additional, Erny, Christian, additional, Fitze, Hansrudolf, additional, Flechsig, Uwe, additional, Follath, Rolf, additional, Frei, Franziska, additional, Gärtner, Florian, additional, Ganter, Romain, additional, Garvey, Terence, additional, Geng, Zheqiao, additional, Gorgisyan, Ishkhan, additional, Gough, Christopher, additional, Hauff, Andreas, additional, Hauri, Christoph, additional, Hiller, Nicole, additional, Humar, Tadej, additional, Hunziker, Stephan, additional, Ingold, Gerhard, additional, Ischebeck, Rasmus, additional, Janousch, Markus, additional, Juranić, Pavle, additional, Jurcevic, Mario, additional, Kaiser, Maik, additional, Kalantari, Babak, additional, Kalt, Roger, additional, Keil, Boris, additional, Kittel, Christoph, additional, Knopp, Gregor, additional, Koprek, Waldemar, additional, Lemke, Henrik, additional, Lippuner, Thomas, additional, Llorente Sancho, Daniel, additional, Löhl, Florian, additional, Lopez-Cuenca, Carlos, additional, Märki, Fabian, additional, Marcellini, Fabio, additional, Marinkovic, Goran, additional, Martiel, Isabelle, additional, Menzel, Ralf, additional, Mozzanica, Aldo, additional, Nass, Karol, additional, Orlandi, Gian, additional, Ozkan Loch, Cigdem, additional, Panepucci, Ezequiel, additional, Paraliev, Martin, additional, Patterson, Bruce, additional, Pedrini, Bill, additional, Pedrozzi, Marco, additional, Pollet, Patrick, additional, Pradervand, Claude, additional, Prat, Eduard, additional, Radi, Peter, additional, Raguin, Jean-Yves, additional, Redford, Sophie, additional, Rehanek, Jens, additional, Réhault, Julien, additional, Reiche, Sven, additional, Ringele, Matthias, additional, Rittmann, Jochen, additional, Rivkin, Leonid, additional, Romann, Albert, additional, Ruat, Marie, additional, Ruder, Christian, additional, Sala, Leonardo, additional, Schebacher, Lionel, additional, Schilcher, Thomas, additional, Schlott, Volker, additional, Schmidt, Thomas, additional, Schmitt, Bernd, additional, Shi, Xintian, additional, Stadler, Markus, additional, Stingelin, Lukas, additional, Sturzenegger, Werner, additional, Szlachetko, Jakub, additional, Thattil, Dhanya, additional, Treyer, Daniel, additional, Trisorio, Alexandre, additional, Tron, Wolfgang, additional, Vetter, Seraphin, additional, Vicario, Carlo, additional, Voulot, Didier, additional, Wang, Meitian, additional, Zamofing, Thierry, additional, Zellweger, Christof, additional, Zennaro, Riccardo, additional, Zimoch, Elke, additional, Abela, Rafael, additional, Patthey, Luc, additional, and Braun, Hans-Heinrich, additional

Published
2017
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33. Tracking the coherent generation of polaron pairs in conjugated polymers

Author

De Sio, Antonietta, primary, Troiani, Filippo, additional, Maiuri, Margherita, additional, Réhault, Julien, additional, Sommer, Ephraim, additional, Lim, James, additional, Huelga, Susana F., additional, Plenio, Martin B., additional, Rozzi, Carlo Andrea, additional, Cerullo, Giulio, additional, Molinari, Elisa, additional, and Lienau, Christoph, additional

Published
2016
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35. Effective detection of weak terahertz pulses in electro-optic sampling at kilohertz repetition rate

Author

Krauspe, Philipp, Banerji, Natalie, and Réhault, Julien

Abstract

The standard terahertz (THz) detection mechanism known as electro-optic sampling can be improved in sensitivity by biasing the polarization of the sampling field. In this work, we show theoretically and experimentally how weak signals can be amplified without inducing distortions. Our study identifies the influence of THz field strength, the polarization quality, and biasing amplitude on signal amplification and distortion. Here we present a distortion-free amplification of a factor of 28 while at the same time reducing the measurement time significantly.

Published
2020

40. 2D IR spectroscopy with phase-locked pulse pairs from a birefringent delay line

Author

Réhault, Julien, Maiuri, Margherita, Manzoni, Cristian, Brida, Daniele, Helbing, Jan; https://orcid.org/0000-0003-3911-8519, Cerullo, Giulio, Réhault, Julien, Maiuri, Margherita, Manzoni, Cristian, Brida, Daniele, Helbing, Jan; https://orcid.org/0000-0003-3911-8519, and Cerullo, Giulio

Published
2014

43. Hydration dynamics of aqueous nitrate

Author

Thøgersen, Jan, Réhault, Julien, Odelius, Michael, Ogden, Tom, Jena, Naresh K, Jensen, Svend J Knak, Keiding, Søren R, Helbing, Jan, Thøgersen, Jan, Réhault, Julien, Odelius, Michael, Ogden, Tom, Jena, Naresh K, Jensen, Svend J Knak, Keiding, Søren R, and Helbing, Jan

Abstract

Aqueous nitrate, NO3–(aq), was studied by 2D-IR, UV–IR, and UV–UV time-resolved spectroscopies in combination with molecular dynamics (MD) simulations with the purpose of determining the hydration dynamics around the anion. In water, the D3h symmetry of NO3– is broken, and the degeneracy of the asymmetric-stretch modes is lifted. This provides a very sensitive probe of the ion–water interactions. The 2D-IR measurements reveal excitation exchange between the two nondegenerate asymmetric-stretch vibrations on a 300-fs time scale concomitant with fast anisotropy decay of the diagonal-peak signals. The MD simulations show that this is caused by jumps of the transition dipole orientations related to fluctuations of the hydrogen bonds connecting the nitrate ion to the nearest water molecules. Reorientation of the ion, which is associated with the hydrogen-bond breaking, was monitored by time-resolved UV–IR and UV–UV spectroscopy, revealing a 2-ps time constant. These time scales are very similar to those reported for isotope-labeled water, suggesting that NO3–(aq) has a labile hydration shell.

Published
2013

44. Linear dichroism amplification: Adapting a long-known technique for ultrasensitive femtosecond IR spectroscopy

Author

Réhault, Julien; https://orcid.org/0000-0002-6565-3016, Zanirato, V, Olivucci, M, Helbing, J, Réhault, Julien; https://orcid.org/0000-0002-6565-3016, Zanirato, V, Olivucci, M, and Helbing, J

Abstract

We demonstrate strong amplification of polarization-sensitive transient IR signals using a pseudo-null crossed polarizer technique first proposed by Keston and Lospalluto [Fed. Proc. 10, 207 (1951)] and applied for nanosecond flash photolysis in the visible by Che et al. [Chem. Phys. Lett. 224, 145 (1994)]. We adapted the technique to ultrafast pulsed laser spectroscopy in the infrared using photoelastic modulators, which allow us to measure amplified linear dichroism at kilohertz repetition rates. The method was applied to a photoswitch of the N-alkylated Schiff base family in order to demonstrate its potential of strongly enhancing sensitivity and signal to noise in ultrafast transient IR experiments, to simplify spectra and to determine intramolecular transition dipole orientations.

Published
2011

46. Hydration Dynamics of Aqueous Nitrate

Author

Thøgersen, Jan, primary, Réhault, Julien, additional, Odelius, Michael, additional, Ogden, Tom, additional, Jena, Naresh K., additional, Jensen, Svend J. Knak, additional, Keiding, Søren R., additional, and Helbing, Jan, additional

Published
2013
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50. Bridged Photochromic Diarylethenes Investigated by Ultrafast Absorption Spectroscopy: Evidence for Two Distinct Photocyclization Pathways

Author

Aloïse, Stéphane, primary, Sliwa, Michel, additional, Pawlowska, Zuzanna, additional, Réhault, Julien, additional, Dubois, Julien, additional, Poizat, Olivier, additional, Buntinx, Guy, additional, Perrier, Aurélie, additional, Maurel, François, additional, Yamaguchi, Shouhei, additional, and Takeshita, Michinori, additional

Published
2010
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