Ultrafast Molecular Dynamics · 2020. 4. 3. · Single Molecule Spectroscopy (a) Slow ion High...
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Ultrafast Solid State Dynamics Ultrafast Molecular Dynamics Single Molecule Spectroscopy (a) Slow ion High Harmonic Generation (HHG) The electric field from a femtosecond NIR laser pulse tunnel ionizes an electron away from the nucleus of an atom. Half an optical cycle later when the electric field of the laser reverses direction, the electron is accelerated back towards the nucleus, coherently emitting an XUV photon, with energy that is an odd- order harmonic of the original NIR. http://www.jaslab.ca/atto2_e.html Man-Nung, Ruoyi We investigate charge carrier dynamics in semiconductor nanostructures at the single molecule limit. Transfer, trapping and recombination of charges can be studied in individual molecules using a combination of confocal fluorescence microscopy and time-correlated single photon counting. These techniques are being used to study emerging, all-inorganic perovskite materials. Fluorescence Spectroscopy of Semiconductor Nanostructures 2 μm Single CsPbBr 3 perovskite nanowires exhibit low-threshold and wavelength- tunable lasing, which persists over one billion excitation cycles, even in ambient atmosphere, demonstrating unprecedented stability in perovskite nanowires. Charge carrier trapping leading to fluorescence intermittency or blinking is being studied in CsPbBr 3 nanocubes and nanoplates. E E In this experiment we investigate the ultrafast charge carrier dynamics at three different interfaces, i.e. semiconductor-gas phase, semiconductor-metal, and semiconductor-semiconductor, by monitoring the full suite of steps from charge excitation to charge separation and subsequent charge recombination. Here is presented an experiment in which the charge carrier dynamics at the n-TiO 2 /p-Si(100) interface is investigated. Charge carrier dynamics at the n-TiO 2 /p-Si(100) interface Bethany, Tymur Ultrafast Charge Carrier Dynamics at Semiconductor Interfaces Attosecond transient absorption spectroscopy ma ps out curve-crossing dynamics in iodinemonobrom ide (IBr). In the experimental results, the diabatic a nd adiabatic pathways at the avoided crossing are r evealed to exhibit continuous/discontinuous evolut ions in the transient absorption, and the ab-initio si mulations provide unambiguous confirmation of th e state assignments. The near-degenerate electroni c states at the avoided crossing are successfully res olved thanks to the special capability of core-level a bsorption to probe orbital-specific information; spe cifically, orbital vacancy is switching between σ ↔ π/π*. Yuki, Kristina, Sonia, Jaden Attosecond Electronic Dynamics in Molecules Ashley, Yen-Cheng, James, Sarvesh We utilize XUV attosecond pulses in conjunction with noncollinear NIR pulses to generate nonlinear wave mixing emission signals, allowing for highly selective, background-free measurements of coherent superpositions of electronic states. The delay dependent FWM emission signal generated from krypton’s 3p 5 ( 2 P 1/2 )nd/ns autoionizing states reveals NIR-induced coupling of bright nd and ns states as well as lifetime-dependent decays. With the development of a pulse shaping apparatus for multidimensional experiments, this technique will be extended to dynamic ultrafast processes in more complex systems. Attosecond Wave Mixing Spectroscopy Ultrafast Charge Carrier Dynamics by XUV Transient Absorption Ilana, Tyler We study the charge carrier dynamics in semiconductor materials after excitation by visible light. Transient XUV absorption spectroscopy has advantages of element/chemical valence specificity and low femtosecond temporal resolution, which is suitable to study ultrafast carrier migration and lattice deformation processes in semiconductor heterostructures. Hole migration across a Si:TiO 2 :Ni heterojunction is observed to occur via initial ballistic transport into the Ni layer, followed by back- diffusion through Ti 3+ defects. The silicon transient XUV spectrum can be decomposed into signals caused by carriers, lattice deformations, and core- hole effects. The valley dependent carrier relaxation dynamics of Si are observed, and the phonon scattering timescales are compared with a Si nanoparticle sample. Ultrafast small polaron formation is observed in a variety of iron oxides. Si Thin film Si Nanoparticles Iron oxide nanorods Silicon Silicon Attosecond Solid State XUV Transient Absorption Hung-Tzu, Juwon New Attosecond Projects (planned) Molecular and solid-state spectroscopy at the carbon K-edge Andrew, Lou, Jason High-harmonic generation Recombination with pump pulse (IR to visible) Sample interaction Soft X-ray spectrometer A new beamline is being developed in the soft X-ray region (200-400 eV) with attosecond resolution, allowing transitions of the carbon 1s to valence orbitals and enabling observation of ultrafast electron dynamics, such as conical intersections, ionization, and vibrations in small organic molecules and lattice changes in diamond and graphene. Diamond K-edge absorption SF 6 Vibration + Ionization Attosecond Solid State XUV Transient Absorption Electron cooling dynamics in nickel Carrier and phonon dynamics in MoTe 2 Mo holes Te holes Te conduction band Edge shifts Decay of core excitons in NaCl Femtosecond X-ray Spectroscopy of Photochemical Reactions Chris X., Val, Eric Ultrafast heterocyclic ring opening of furfural shows core to nonbonding orbital of open-chain carbene intermediate within 350 fs. The lack of recovery of 1 ∗ ground state depletion shows that the internal conversion back to ground state is minor. The evolution of the core-to-valence resonances shows an ultrafast population transfer to T 1 state in acetylacetone via intersystem crossing on a 1.5±0.2 ps time scale after ultraviolet excitation. Romain Novel experimental schemes are being developed to probe additional degrees of freedom in materials. New capabilities include 1) the generation of circularly polarized attosecond pulses, providing access to spin dynamics in magnetic multilayers, 2) time-resolved XUV diffraction experiments and 3) cryo-cooling of samples, allowing the study of intriguing properties of topological insulators, phase transitions and strongly correlated materials. Interface-sensitive scattering Electron and Spin Dynamics of Quantum Matter Attosecond circular dichroism: exploring new coherent spin phenomena Attosecond XUV Transient Reflectivity Romain Transient reflectivity gives experimental access to the complex-valued index of refraction n or to the dielectric function. Additionally, reflection measurements allow access to single crystal samples, and can provide surface sensitivty (1-10nm) by tuning angle of incidence. Electronic properties Attosecond transient reflectivity reveals dynamics of core- excitons in MgO, quasiparticles with lifetimes below 3 fs. Structural properties In monocrystalline bismuth, XUV transient reflectivity allows to follow the motion of coherent phonons triggered by a laser pulse.
Transcript of Ultrafast Molecular Dynamics · 2020. 4. 3. · Single Molecule Spectroscopy (a) Slow ion High...
Ultrafast Solid State Dynamics
Ultrafast Molecular Dynamics
Single Molecule Spectroscopy
(a) Slow ion
High Harmonic Generation (HHG)
The electric field from a femtosecond NIR laser pulse tunnel ionizes an electron away from the nucleus of an atom. Half an optical cycle later when the electric field of the laser reverses direction, the electron is accelerated back towards the nucleus, coherently emitting an XUV photon, with energy that is an odd-order harmonic of the original NIR.
http://www.jaslab.ca/atto2_e.html
Man-Nung, Ruoyi
We investigate charge carrier dynamics in semiconductor nanostructures at the single molecule limit. Transfer,trapping and recombination of charges can be studied in individual molecules using a combination of confocalfluorescence microscopy and time-correlated single photon counting. These techniques are being used to studyemerging, all-inorganic perovskite materials.
Fluorescence Spectroscopy of Semiconductor Nanostructures
2 μm
Single CsPbBr3 perovskite nanowiresexhibit low-threshold and wavelength-tunable lasing, which persists over onebillion excitation cycles, even inambient atmosphere, demonstratingunprecedented stability in perovskitenanowires.
Charge carrier trapping leading tofluorescence intermittency or blinkingis being studied in CsPbBr3 nanocubesand nanoplates.
EE
In this experiment we investigate the ultrafast charge carrierdynamics at three different interfaces, i.e. semiconductor-gasphase, semiconductor-metal, and semiconductor-semiconductor,by monitoring the full suite of steps from charge excitation tocharge separation and subsequent charge recombination. Here ispresented an experiment in which the charge carrier dynamics atthe n-TiO2/p-Si(100) interface is investigated.
Charge carrier dynamics at the n-TiO2/p-Si(100) interface
Bethany, Tymur
Ultrafast Charge Carrier Dynamics at Semiconductor Interfaces
Attosecond transient absorption spectroscopy maps out curve-crossing dynamics in iodinemonobromide (IBr). In the experimental results, the diabatic and adiabatic pathways at the avoided crossing are revealed to exhibit continuous/discontinuous evolutions in the transient absorption, and the ab-initio simulations provide unambiguous confirmation of the state assignments. The near-degenerate electronic states at the avoided crossing are successfully resolved thanks to the special capability of core-level absorption to probe orbital-specific information; specifically, orbital vacancy is switching between σ ↔π/π*.
Yuki, Kristina, Sonia, Jaden
Attosecond Electronic Dynamics in Molecules
Ashley, Yen-Cheng, James, Sarvesh
We utilize XUV attosecond pulses in conjunction with noncollinear NIR pulses to generate nonlinear wave mixing emission signals, allowing for highly selective, background-free measurements of coherent superpositions of electronic states. The delay dependent FWM emission signal generated from krypton’s 3p5(2P1/2)nd/ns autoionizing states reveals NIR-induced coupling of bright nd and ns states as well as lifetime-dependent decays. With the development of a pulse shaping apparatus for multidimensional experiments, this technique will be extended to dynamic ultrafast processes in more complex systems.
Attosecond Wave Mixing Spectroscopy
Ultrafast Charge Carrier Dynamics by XUV Transient Absorption
Ilana, Tyler
We study the charge carrier dynamics in semiconductor materials after excitation by visiblelight. Transient XUV absorption spectroscopy has advantages of element/chemical valencespecificity and low femtosecond temporal resolution, which is suitable to study ultrafast carriermigration and lattice deformation processes in semiconductor heterostructures.
Hole migration across a Si:TiO2:Ni heterojunction is observed to occur via initial ballistic transport into the Ni layer, followed by back-diffusion through Ti3+ defects.
The silicon transient XUV spectrum can be decomposed into signals caused by carriers, lattice deformations, and core-hole effects. The valley dependent carrier relaxation dynamics of Si are observed, and the phonon scattering timescales are compared with a Si nanoparticle sample.
Ultrafast small polaron formation is observed in a variety of iron oxides.
Si Thin film
Si Nanoparticles
Iron oxide nanorods
Silicon
Silicon
Attosecond Solid State XUV Transient Absorption
Hung-Tzu, Juwon
New Attosecond Projects
(planned)
Molecular and solid-state spectroscopyat the carbon K-edge
Andrew, Lou, Jason
High-harmonic generation
Recombination with pump pulse (IR to visible)
Sample interaction
Soft X-ray spectrometer
A new beamline is being developed in the soft X-ray region (200-400 eV)with attosecond resolution, allowing transitions of the carbon 1s tovalence orbitals and enabling observation of ultrafast electron dynamics,such as conical intersections, ionization, and vibrations in small organicmolecules and lattice changes in diamond and graphene.
Diamond K-edge absorption SF6 Vibration + Ionization
Attosecond Solid State XUV Transient AbsorptionElectron cooling dynamics in nickel
Carrier and phonon dynamics in MoTe2
Moholes
Teholes
Te conduction bandEdge shifts
Decay of core excitons in NaCl
Femtosecond X-ray Spectroscopy of Photochemical Reactions
Chris X., Val, Eric
Ultrafast heterocyclic ring opening of furfuralshows core to nonbonding orbital of open-chaincarbene intermediate within 350 fs. The lack ofrecovery of 1𝑠𝜋∗ground state depletion showsthat the internal conversion back to groundstate is minor.
The evolution of the core-to-valence resonancesshows an ultrafast population transfer to T1 statein acetylacetone via intersystem crossing on a1.5±0.2 ps time scale after ultraviolet excitation.
Romain
Novel experimental schemes are beingdeveloped to probe additional degrees offreedom in materials. New capabilitiesinclude 1) the generation of circularlypolarized attosecond pulses, providing accessto spin dynamics in magnetic multilayers,2) time-resolved XUV diffraction experimentsand 3) cryo-cooling of samples, allowing thestudy of intriguing properties of topologicalinsulators, phase transitions and stronglycorrelated materials.
Interface-sensitive scattering
Electron and Spin Dynamics of Quantum Matter
Attosecond circular dichroism: exploring new coherent spin phenomena
Attosecond XUV Transient Reflectivity
Romain
Transient reflectivity gives experimental access to the complex-valuedindex of refraction n or to the dielectric function. Additionally, reflectionmeasurements allow access to single crystal samples, and can providesurface sensitivty (1-10nm) by tuning angle of incidence.
Electronic propertiesAttosecond transient reflectivityreveals dynamics of core-excitons in MgO, quasiparticleswith lifetimes below 3 fs.
Structural propertiesIn monocrystalline bismuth,XUV transient reflectivity allowsto follow the motion of coherentphonons triggered by a laserpulse.
