1. Department of Chemistry UIUC (Vura-Weis group)
Impact of “Spatial Chirp” in High Harmonic Extreme Ultraviolet (XUV) Light Source for Thin-Film Core-Level Spectroscopy
Ming-Fu Lin
Department of Chemistry
UIUC (Vura-Weis group)
Introduce myself
Slowly introduce the “Title of the talk”, and mention it is different
Spatial chirp here is defined as the ”variation of spatial distribution” in the XUV energy component! Morphology and homogeneity of the thin-film
Table top light source offer Temporal-elemental resolution in the molecular system we are going to study.
June 25, 2015 ISMS, UIUC

2. Instrument Vertical (y) XUV Energy Horizontal (x) pinhole scan
35 fs
800nm
NIR
peak intensity
6×1014 W/cm2
pinhole scan
Spatio-Spectral information (x, y, E)
XUV Energy
Vertical (y)
Horizontal (x)
reduce the time on explaining the HHG, keep time on the idea and why we do this experiments
Specify that we only use “top beam” for the absorption experiments

3. Pinhole Scan at Focus for Spatio-Spectral Information
Focal spot size for all the XUV energy. It can be fitted by a Gaussian function and 2W is 125um and 152um in vertical and horizontal, respectively.
If now we draw the figure along the spectral axis, and look into its spatial distribution.

4. Spatial Chirp on the XUV Light Source
We show the spatio-spectral information in the spectra axis and disintegrate the spectral region into Valley, peak 1 and peak 2 region.
Different energy illuminates at different sample area on the thin-film. And if the film is not uniform, we will have a problem in the absorption experiments.

5. New Aspect in Beer’s Law
Spatio-Spectral information at focus
& Sample morphology,
& Absorption cross-section
In order to test this theory, we use a sample which has a known morphology and absorption cross-section to convolute with out spatial-spectral information.
Finally to compare our simulation with the experimental results.
Simulated Optical Density

6. Test of Concept Using Patterned Si3N4 Film 70 μm 35 nm 25 μm 235 nm
XUV diameter
~ 130 μm
Using patterned Si3N4 to test our idea. Flat Si3N4 itself has broad absorption feature. No resonant peaks at all.
Point out the phase is opposite.

7. PbI2 (lead iodide) Thin-Film Sample from Spin-Coating
Iodine (4d, N-edge)
The harmonic structure noise is the same amplitude of the resonant feature.

8. Organic Metallic Thin-Film, C32H72N2CoCl4 from Spin-Coating
Co (3p, M-edge)
At 10% of Gaussian amplitude, the noise the same size of the pre-peak.

9. “Transient Morphology” in the Pump-Probe Experiment
6% Excited state
Fe2O3
Thin-film/
Transient
absorption spectrum
J. Phys. Chem. Lett., 
2013, 4 (21),
pp 3667–3671

10. ACKNOWLEDGEMENTS Prof. Josh Vura-Weis Department of Chemistry, UIUC
Graduate students
Kristin Benke
Michaela Carlson
Liz Ryland
Max Verkamp
Kaili Zhang
Funding sources
Air Force office scientific research
UIUC start up
VISIT our lab at A227, CLSL

11. High-Order Harmonic Generation
Nature Photonics (2011)