Femtosecond Molecular Dynamics

Ultrafast Solid State Spectroscopy using High Harmonic Generation

Ultrafast Gas Phase Spectroscopy using High Harmonic Generation

Single Molecule Spectroscopy

Attosecond Dynamics in Solid State MaterialsWith attosecond resolution, we can observe electron and hole dynamics before lattice motion occurs.

Ultrafast Charge Carrier Dynamics by XUV Transient Absorption

Lucas, Scott

Transition state dynamics of prototypical alkyl iodide photodissociation reactions are investigated throughthe direct observation of the transient valence electronic structure in the vicinity of the iodine reporter atom.

Andrew, Aditi, Kirsten Marina, Kirsten

Photodissociation dynamicsof CH3I will be explored by afemtosecond soft X-rayprobe pulse following a UVpump pulse. Photoelectronsfrom the core shell will bemonitored by Velocity MapImaging as below to retrievebinding energy and angulardistribution.

Adam, Florian

Ring opening mechanismsin aromatic heterocycles such as selenophene and thiopheneare probed using 2p and 3d inner shell absorption features.The technique exploits the sensitivity of XUV absorptionspectroscopy to the C-Se and C-S bonding.

Natalie, Eunice

(a) Slow ion

Electron Motion in Atoms and MoleculesHigh 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

Erika, Ashley, Wei

Hung-Tzu, Michael, Lauren, Marieke, Chris, Peter

holes

electrons

Transient absorption spectroscopyin Ge tracks both electron and holedynamics simultaneously.

VO2 exhibits an ultrafast insulator to metal phase transition upon heating and ultrafast excitation. By separatingelectronic dynamics from lattice motion, we seek to understand the mechanism of the phase transition, which is stillwidely debated.

V O

Vanadium 3p ---------

MetalInsulator

Sample Grating

Mirror

Absorption:(current

experiments)

Reflection:coming soon!

CCDCamera

By developing transient reflectivity, we hope to expand our studiesto materials such as gallium arsenide and 2D transition metaldichalcogenides.

Carbon K-edge Spectrum of N-Parylene

Extension of the HHG source to the Carbon K-edge (~285 eV)has been achieved, opening up a new class of studies exploringfundamental hydrocarbon photochemistry, non-Born-Oppenheimerdynamics, dissociative and bound wavepacket dynamics, and radicalspectroscopy through femtosecond time-resolved NEXAFS.

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.

We study the charge carrier dynamics in semiconductor materials after excitation by visible light. Transient XUVabsorption spectroscopy has advantages of element/chemical valence specificity and low femtosecond temporalresolution, which is suitable to study ultrafast electron migration processes in semiconductor heterostructures.

Based on the match betweenexperimental results andcharge transfer multipletsimulation, the excited-statecharacter of α-Fe2O3 afterabsorbing a 400 nm photoncan be assigned to a LMCTstate.

Hole-transfer processfrom photo-excitedCo3O4 to methanol isstudied by the designof an in situ liquidflow cell. The kineticsshow that CH3OH actsas a hole scavengerafter photoexcitation.

x3

We use an isolatedattosecond pulse centered at15 eV to create a coherentsuperposition of Rydbergstates in nitrogen. Quantumbeating between states in thesuperposition with periods asshort as 1.3 fs is revealed bytime-delayed NIR photonsthat transfer population toneighboring levels. We willextend this technique tostudy coupled ultrafastelectronic and nucleardynamics in polyatomicmolecules such as CO2 andH2O.

Henry, Mazyar, Yuki

We use isolated attosecond pulses extending from 50 to 75 eV to probe the fastest charge migration dynamics that occur in nature. These dynamics are driven purely by many-body, electronic correlations and can give rise to the transport of charge across an entire molecule on the few femtosecond timescale.

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

Mihai, Brett

Ultrafast Charge Carrier Dynamics at Semiconductor Interfaces