Raúl Baragiola, Engineering Physics Research: Laboratory Astrophysics – optical characterization...

Raúl Baragiola, Engineering PhysicsResearch: Laboratory Astrophysics – optical characterization and simulation of micrometeorite impact via pulsed laser energy deposition.

Fellows:

Mark Loeffler - Simulation of micrometeorite impact on asteroids withpulsed laser beams. Characterization by FTIR andelectron spectroscopy

Devin Pugh - Characterization of thin film growth by diffuse laser scattering, interferometry, and microbalance techniques.Application to microporous amorphous ice.

Ben Teolis - Ultraviolet spectroscopy of ozone production incondensed gases by ion and photon irradiation.Application to icy satellites of Jupiter and Saturn.

Associates:Catherine Dukes, Jan Lorincik

NSF IGERT: Science and Engineering of Laser Interactions with MatterUniversity of Virginia

Mark Loeffler research on space weathering of asteroids

Transient heating of olivine by laser pulse produces changes in near IR absorption bands similar to what is observed on asteroids, and attributed to the impact of micrometeorites and solar wind ions. XPS results show that irradiation forms iron precipitates. Unlike previous research, Mark will do reflectance measurements in situ, to prevent oxidation by air.

Electron microscopy will be used to understand the relationship between Fe nanoparticle size and distribution and the reddening of the mineral due to irradiation.

Lou Bloomfield, Dept. of PhysicsResearch: Dynamics of Cluster Structure, Isomerization, and Photodissociation.

Associates: Andy Dally & Songbai Ye

Photodesorption of Alkali Negative Ions from Alkali-Halide Cluster

Anions

Using picosecond laser pulses, we have examined the photodesorption of negatively charged alkali ions from alkali-halide clusters. These fragile atomic ions, with extra electrons that are only barely held in place, have not been observed previously among the fragments leaving alkali-halide (salt) surfaces following exposure to light.

We find this unusual desorption in a broad class of negatively charge alkali-halide clusters—those containing two or more electrons that are not involved in the salt’s ionic bonding. The desorption starts via electronic excitation, with the excitation decaying quickly to eject the outgoing negative ion.

Thermal Isomerization Dynamics and Melting in Alkali-Halide Clusters

We have produced (a) ensembles of cluster ions with enough thermal energy to undergo rapid changes in geometric structure, a process known as thermal isomerization. Because they switch quickly from one isomeric form to another, these clusters are effectively molten.

To study the dynamics of these clusters, we use an ultrashort laser pulse (b) to selectively destroy most of the clusters in one isomeric form. Thermal isomerization immediately begins to repopulate the missing form. We use a second laser pulse to measure the isomer populations at later times (c), and thus learn about the structure, energetics, and thermal properties of these tiny systems.

James Fitz-Gerald, Dept. of Materials Science and Engineering

Associate:Andrew Mercado - Matrix Assisted Pulsed Laser Evaporation (MAPLE) of Biodegradable Polymers: Excimer (ns) laser processing

Research: Laser based processing of organic and inorganic materials. In-situ plasma characterization, Materials characterization

• The volatile solvent absorbs a large % of the laser pulse. Upon heating, the solvent gently desorbs the organic molecule.

laser pulse

frozen target

volatile solvent is pumped away

substrate

012345678A

itrary

Fluence: 0.30 J/cm2

Laser frequency: 20 Hz30,000 pulses

100 mTorr Ar, 60° tilt

100 nmSi wafer

Fluence: 0.43 J/cm2

Laser frequency: 20 Hz4,000 pulses

100 mTorr Ar

Fluence: 0.18 J/cm2

Laser frequency: 10 Hz10,000 pulses100 mTorr Ar

Fluence: 0.18 J/cm2

Laser frequency: 20 Hz21,000 pulses100 mTorr Ar

(e)(d)

PLGA thin film

NMR spectra (a) comparing the native and deposited thin films and scanning electron microscopy (SEM) images of the deposited thin films (b-e). NMR spectra of the deposited films are in good agreement with the native material, with the exceptions as noted. SEM micrographs show trends in energy and deposition rate, both of which have a direct relationship to the entrainment process.

(PLGA)

3 4[] ]Andrew Mercado’s Research on

MAPLE of a Biodegradable Polymer - PLGA

Thomas Gallagher, Dept. of PhysicsResearch: Interactions of Rydberg atoms with radiation fields and

with each other.

Fellows:Edward Shuman – Dielectronic Recombination in crossed static and

microwave fields.Ken Baranowski - Microwave ionization of alkali atoms.

Associate:Michael Bajema – Control of the branching ratio for autoionization with

the time delay between femtosecond laser pulses.

NSF IGERT: Science and Engineering of Laser Interactions with Matter

University of Virginia

Edward Shuman’s Research on Dielectronic Recombination

Dielectronic Recombination is the recombination of an ion and an electron via an autoionizing Rydberg state. It is enhanced by a static field below the classical limit, but does not occur above the classical limit. Adding a microwave field polarized perpendicular to the static field enables recombination above the classical limit. The mechanism is m transitions to more stable high m states.

Dielectronic Recombination signals with an 11 GHz field polarized perpendicular to a static field. The classical limit is the solid bold line. The signals above the classical limit are not present without the microwave field.

NSF IGERT: Science and Engineering of Laser Interactions with Matter

University of Virginia

0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

-120-100 -80 -60 -40 -20 0

Relative binding energy (cm-1

0.09.919.729.738.548.858.467.078.588.397.6107.4118.7127.2137.8

Static electric field (V/cm

Tatiana Globus, Boris Gelmont, Dept. of Electrical and Computer EngineeringResearch:Terahertz Wave Interaction with Biological Macromolecules (Experiment + Modeling)

Fellow:Tiffany Mapp - Computer modeling of submillimeter wave absorption of short biological molecules.

Associate:Maria Bykhovskaia- Theoretical Prediction of Absorption Spectra.

Tiffany Mapp’s Research on Computer Modeling of Submillimeter Wave Absorption

of Short Biological Molecules

Absorption spectra of double stranded RNA fragments Poly A-Poly U calculated for oscillator decay values =1 cm-1 and =0.5 cm -1 and for two different orientation of electric field of radiation relative to the long axes of a molecule.

THEORETICAL PREDICTION OF ABSORPTION SPECTRA

Torsion angles Frequencies<300 cm -1

Energy minimum Normal modes Spectra

Absorption Spectrum PolyAPolyU (z)= 1

Frequency (cm-1)

0 10 20 30 40 50 60

Absorption of PolyAPolyU = 0.5

Frequency (cm-1)

0 10 20 30 40 50 60

RNA Infra-red active modes have been calculated directly from the base pair sequence and topology of a moleculeSpectra are sensitive to a molecule’s compositionIntense peak is predicted at the lowest frequency ~ 2 cm-1.

() 2 (pk)2 / ( (k2 - 2 )2 + 2 2 )

Absorption spectra are calculated using the normalized dipole moment p

Ian Harrison, Dept. of ChemistryResearch: Laser induced photochemistry and spectroscopy at surfaces,

reaction dynamics of catalysis.

Fellows:Alex Bukoski - Microcanonical rate theory at surfaces: Application to

non-equilibrium laser, electron, and collisionally induced processes at surfaces.

Kristin Buck - Surface photochemistry and spectroscopy: Broadband ir/visible sum frequency generation,ultrafast photochemistry of adsorbates

Associates:Rob Zehr, Neel Samanta - Adsorbate photochemical dynamics: ns lasers.Todd Schwendemann - Electron transfer chemistry of single adsorbates studied by scanning tunneling microscopy.

Alex Bukoski’s Research on Microcanonical Unimolecular Rate Theory at Surfaces

Dissociative chemisorption of a methane molecular beam incident on a Ni(100) surface with and without infrared laser excitation of the 3 antisymmetric C-H stretching vibration of the gas-phase CH4. Comparison of experiment to theory with different reaction threshold energies, E0.

Schematic depiction of the kinetics and energetics of activated dissociative chemisorption. Zero-point energies are implicitly included within the potential energy curve along the reaction coordinate.

CH4 : J = 2 , v3 = 1 Eigenstate

Tn = 400 K

Normal Translational Energy [kJ/mol]

20 30 40 50 60 70

PC - MURTE0 = 67 kJ/mol

E0 = 53 kJ/mol

Bob Jones, Department of PhysicsResearch: Investigating the response of atoms and small molecules to intense short laser pulses and the use of coherent light to view and control quantum dynamics in atoms and molecules

Fellows:Dan Pinkham - Characterization and control of ultra-fast laser pulse shapes for manipulation of intense field fragmentation processes in small molecules and clusters.Brett Sickmiller - Creation of sub-20 femtosecond VUV light pulses from intense near infrared light via high harmonic generation.

Associates:Merrick DeWitt, Eric Wells - Investigation of intense laser ionization and fragmentation in molecules and small clustersSantosh Pisharody, Jason Zeibel, Jeremy Murray-Krezan- Manipulation of electronic wavepackets for probing coherent time-dependent processes in atoms

Pinkham/Well’s Research on Closed Loop Control of Intense Laser Fragmentation of Clusters

Typical results from a control experiment using S8 as a target. The left most columns show the S+ and S2+ product yields using an unshaped 100 fsec laser pulse. The middle and right hand columns show the same product yields when the algorithm is told to optimize the ratios S2+:S+ and S+:S2+, respectively.

Schematic of a closed loop laser control apparatus. A genetic algorithm searches for the “best” laser pulse to optimize a specified laser fragmentation pattern. The algorithm controls a liquid crystal based laser pulse shaper based on feedback from a fragmentation experiment .

Transform S2

+ / S+ S+ / S2

0.0 1.0x10-5 2.0x10-5 3.0x10-5-0.02

1 kHz800 nm120 fsec

James Landers, Dept. of ChemistryResearch: Analytical microchip technology for diagnostics and biomedical research.

Fellows:

James Karlinsey - Precision laser ablation of microstructures in glass chips - Acousto-optic technology development for laser-induced fluorescence detection on microchips

James Karlinsey’s Research on the Development of Microchip Technology

Laser Machining with Femtosecond

Pulses: The SEM shows the exit plane of a microscope slide, after exposure to 2 mJ pulses fired at a 1 kHz repetition from a fs Regen laser focused at 250 mm. The laser-drilled has small dimensions (<100 µm) and will allow for microfluidic connects between different layers in a microdevice.

35 40 45 50 55 60 65

time/sR

514 nm

488 nm 476 nm

457 nm

Multiline Ar+ Laser Scan: The RF applied to the AOTF was scanned from 100-180 MHz (~450-700 nm) at an interval of 0.5 MHz every 0.1 s. This offers new approaches for controlling the addressing of lasers on microchips.

Gabriel Laufer – Mechanical and Aerospace EngineeringResearch: Remote sensing of the distribution of CH4 in the

stratosphere and of oceanic chlorophyll from sounding rockets

Fellows:W. Clayton Nunnally- Wide Field of View Gas Filter Correlation Radiometer for Sounding Rocket Deployment

Clayton Nunnaly’s research on measuring the stratospheric distribution of CH4

Absorption spectra of atmospheric CH4 and HCl, superimposed by the transmission curve of a spectral-limiting bandpass filter. By correlating this spectrum with the absorption by CH4 in a sample cell within the system, optical densities of 0.0001-0.001 atm-m can be measured at an uncertainty of <0.3% and FOV >30 while rejecting HCl interference.

Schematic of the solar gas filter correlation radiometer (GFCR). The system was designed to detect CH4 at high specificity using the absorption spectrum of solar radiation. A wide field of view (FOV) optical collection allows detection during rocket ascent without the need for active control.

Stratospheric Absorbance 3.2-3.4 micronsTemp:233K Pressure: 0.01atm Path 50km

0.00E+00

2.50E-01

5.00E-01

7.50E-01

1.00E+00

3.46 3.38 3.31 3.24WL (m)

Bandpass Filter CH4 HCL

Microscale Heat Transfer LabProfessor Pamela Norris

Department of Mechanical and Aerospace Engineering

Research: • Observe transient carrier phenomena on a subpicosecond timescale using

non-destructive optical techniques.200 femtosecond laser in a pump-probe setup

• Contribute to the foundation for the continued development of nanoscale technologies.

Measure critical properties of metals and semiconductorsDevelop and verify models of transient carrier phenomena

• Fellow:Rob Stevens - Ultrafast carrier dynamics in a-Si:H and energy

transport in thin metallic films.

Rob Stevens’ Research on Ultrafast Carrier Dynamics in a-Si:H Films

Chopper 500 HzPhotodetector

Prism on micropositioning

stage (0.1 m res.)

1 kHz, ~100 fs, 625-1000nm, 20-120J

Probe:

1 kHz, ~100 fs, white light

Computer

Sample

Lock-in Amp

-1 0 1 2 3 4 5 6

1.426 eV1.551 eV1.591 eV1.611 eV1.632 eV1.654 eV1.677 eV1.700 eV

Time (ps)

Devising optical pump-probe techniques and models to better understand the transient carrier phenomena of a-Si:H films used by the photovoltaic industry. Primary focus is on recombination mechanisms and the role of band tail states.

Below is a series transmission scans of intrinsic a-Si:H collected using varying probe energies. The decays indicated by scans are a combination of thermalization of hot electrons, recombination, and trapping.

Brooks H. Pate, Dept. of ChemistryResearch: unimolecular isomerization kinetics, solvent effects on intramolecular vibrational dynamics, dynamic rotational spectroscopy

Fellows:Pam Crum (2nd Year) - Reaction dynamics in gas and solution by

selective-excitation, broadband probe ultrafast IR spectroscopy (ps pump - fs probe)

Kevin Douglass (2nd Year) - Time-domain 2D-Microwave spectroscopy of high-energy isomerization reactions (using

Fourier transform signal acquisition) Associates:John Keske (Ph.D. 2001) - Rotational spectroscopy of isomerizing

moleculesHyun Yoo (Ph.D. 2002) - Vibrational dynamics in gas and solutionYehudi Self-Medlin (Ph.D. 2003) - Vibrational dynamics and

isomerization in gas and solution

log(3330cm-1)0 1 2 3 4

3 IVRThreshold

kIVR (1011 s-1)0.0 0.5 1.0 1.5 2.0 2.5 3.0

CCl4kVER = (67 ps)-1

kTOT = kIVR + kVER

Competition BetweenIntramolecular and Solution Dynamics

kIVR 0 10 20 30 40 50Abs

Time (ps)0 5 10 15 20

4Acetylenic CH Stretch

C6H5CCH

0 30 60 90 120 150

3 OH StretchCD3OH

OH Stretch(CF3)3COH

Direct Comparison ofGas- and Solution-Phase Dynamics

MW Frequency Scan to Measure303 - 202 Rotational Transition

Frequency (MHz)

26358.5 26359.5 26360.5

FTMW 111 - 202 Excited

State Transition

Frequency (MHz)13647.10 13647.75 13648.40

Rotational Spectroscopy of Excited States by IR - FTMW - MW Triple Resonance Spectroscopy

Level Diagram for Fluoroproyne

FTMW Monitor(13647.75)

MW Scan

IR(3332.26 cm-1)

(JKaKc)

Using the SELIM Ultrafast Laser Facility we have performed the first direct comparison of the isolated molecule and solution phase vibrational energy relaxation rates of polyatomic molecules. We find that solvent effects are minor and that the total relaxation rate in solution is dominated by the purely intramolecular dynamics. (Second plot: Gas (black), 0.05 M CCl4 solution (red))

The first measurements of the rotational spectrumof a laser-prepared vibrational excited state byFourier transform microwave (FTMW) spectroscopy is shown. This technique has also been extended to include IR-MW-MW triple-resonance measurements.

Vibrational Dynamics by Ultrafast Infrared Spectroscopy andDynamic Rotational Spectroscopy

Olivier Pfister, Dept. of PhysicsResearch: Quantum Optics and Quantum Information; experimental and theoretical studies of continuous-variable entanglement.

Fellows:

Raphael Pooser, 2nd year Engineering Physics student (Ph.D.)

- Theory of interferometry at the Heisenberg limit. - Design of a three-photon optical parametric oscillator and experimental investigation of its quantum and classical properties.

Gregory Jennings, 2nd year Material Science Engineering student (M.S.)

- Study and characterization of periodically poled nonlinear optical ferroelectrics.

Darrell Gullatt, 1st year Engineering Physics student (Ph.D.)

- Laser frequency stabilization and characterization.

QUANTUM OPTICS/QUANTUM INFORMATION Pfister Labs, UVa Physics

• Entanglement of two quantum optical fields: Quantum teleportation: “the disembodied transfer of an

unknown quantum state from one location to another” Ultra-precise interferometry at the Heisenberg limit:

measure optical phase

(N=photon number)

Time-domain: ultrasensitive detection of phase shifts (e.g. gravitational waves)

Space-domain: ultra-high-resolution quantum imaging / quantum lithography.

• Entanglement of three quantum optical fields: Quantum error correction and parallel quantum

communication (quantum telecloning).

Cass Sackett, Dept. of PhysicsResearch: Laser cooling, Bose-Einstein condensation, and atom interferometry

Fellow:Jessica Reeves -Bose-Einstein condensation: Development of BEC machine, application to atom-interferometric measurement of inertial and interaction effects.

Jessica Reeves’s Research on Bose-Einstein Condensation and Atom Interferometry

Vacuum chamber constructed for BEC experiment. Currently trapping ~109 atoms at T ~ 50 K, and transferring atoms to UHV cell for further cooling.

Schematic depiction of atom interferometry with a Bose-Einstein condensate. A stationary cloud of atoms can be split into two pieces using laser manipulation, and later recombined. The atomic wave function will exhibit interference fringes that depend on the phase difference experienced.

Suely Black, Department of Chemistry and CMR Research: Ab initio electronic structure modeling of infinite structures by van der Waals and covalent clusters

Fellows:Cheryl Blumenberg -Theoretical study of urea clusters structures and vibrational spectra using Hartree-Fock, DFT, and MP2 methods.Kendra Brown - Determination of the electrostatic potential of the hydrogen- terminated Si(100) 2x1 surface by ab inito methods for adsorption studies.Charmagne Harris - Calculation of the static first hyperpolarizabilities of methyl-nitroaniline (MNA) clusters.Associates:Chalette Sapp-Mobley - Theoretical study of the adsorption of MNA on the hydrogen-terminated Si(100) 2x1 surface.Sheena Inge - Application of semi-empirical/ab initio hybrid methods to model the Si(100) 2x1 surface.

NSF IGERT: Science and Engineering of Laser Interactions with MatterNorfolk State University

Blumenberg’s urea cluster structure determination using HF, DFT and MP2 methods

Clusters of up to seven urea molecules optimized with selected degrees of freedom to reproduce the crystal arrangement. Relative internal molecular coordinates are allowed to change. The OCNH dihedral angle decreases with increasing cluster size, approaching zero, which corresponds to the value found in the crystal.

0 1 2 3 4 5 6 7 8

Allowed degrees of freedom in geometry optimization

Internal Dihedral Angle (º) OCNH, 6-31G** HF Optimized Geometries

# molecules in cluster

Carl Bonner, Department of Chemistry and CMR

Research: Investigating the 1st and 2nd order hyperpolarizability of molecular chromophores and polymers and the response transformation from individual molecules to clusters to films. Fellows:

LaQuita Huey – Measurement of two photon absorptivities in a range of thiacyanine analogues for optical limiting applications at Ti-Sapphire wavelengths

Associates:Olu Bolden - Characterization of 1st hyperpolarizbility of chromophores chiral or other tertiary structures, such as Ni-salophen (binapthol) compounds

HyperRayleigh Scattering Measuerments of the 1st Hyperpolariability of Ni Salophen

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

Slope = 3.8443 x 10-38

Slope = 1.05443 x 10-41

pNA reference DR-19

Number Density (particle/cm3) x 10

The dependence of the signal on concentration (expressed as number density) gives the molecular hyperpolarizbility. Measurements are made relative to a standard compound para-nitrobenzene.

Schematic of HyperRayleigh Scattering (HRS) experiment. The experiment measures the intensity of the second harmonic of the Rayleigh scattered line. This intensity is proportional to the square of the incident intensity. A confocal cavity maximizes the collection efficiency.

The signal is

I(2) = G i Ni<HRS2>i I()2

which for a two component system of solute and solvent is

=G[ Ns<HRS2>s + Nc<HRS

2>c ] I()2

chopper

lens beamdump

Lock-in ampref

Ar+ ion pumped AmplifiedTi-Sapphire Laser, 800 nm

150 fsec, 250kHz, 4 J

ComputerBPF

IFattenuator

0.0 0.5 1.0 1.5 2.0 2.5

12 Signal of 21 mM (V)

Signal of 12 mM (V)

Signal of 7 mM (V)

I() (watt/cm2) x 1011

Mikhail A. Noginov Department of Physics and CMRResearch: The effect of the diameter of the pumped spot on the threshold and the slope efficiency of Nd0.5La0.5Al3(BO3)4 ceramic random powder lasers

Fellows:Kaleem J. Morris, MS student (directly supported by IGERT)

Associates:G. Zhu, MS student (not supported by IGERT directly)M. Bahoura, research faculty (not supported by IGERT directly)

Study of random laser emission at different sizes of the pumped spot

Experimental setup

0 10 20

Pumping energy (mJ)

0.001 0.01 0.1 1Diameter (cm)

Slope=1

Input/Output curves

Threshold density vs. spot diameter

Raúl Baragiola, Engineering Physics Research: Laboratory Astrophysics – optical characterization...

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