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Ultrafast Terahertz Kerr Effect Spectroscopy: Detection of Intramolecular Vibrational Coherences...
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Ultrafast Terahertz Kerr Effect Spectroscopy: Detection of Intramolecular Vibrational Coherences Marco Allodi, Ian Finneran , Geoffrey Blake California Institute of Technology
Transcript of Ultrafast Terahertz Kerr Effect Spectroscopy: Detection of Intramolecular Vibrational Coherences...
Ultrafast Terahertz Kerr Effect Spectroscopy:Detection of Intramolecular Vibrational
Coherences
Marco Allodi, Ian Finneran, Geoffrey BlakeCalifornia Institute of Technology
Nonlinear THz spectroscopy is very difficult!
Electronics Lasers (Photonics)
Sizov, Fedir F., et al. Optical Engineering 52.3 (2013)
Multi-dimensional NMR
13C
1H
15N
1H2D-IR and optical experiments
2D Spectroscopies are nonlinear
Milestones Necessary for 2D THz Spectroscopy
Generate Coherences
Manipulate Coherences
Detect Coherences
Terahertz spectra are complicated, and sensitive to intermolecular structure
McGuire et al, in preparation.
Brett McGuire RI14
Teraherz Kerr Effect
Hoffmann, M. C. et al. Appl. Phys. Lett., 2009, 95, 231105.
n
n = n + Δn
E
The only molecular, ultrafast, nonlinear THz spectroscopy
The Optical Kerr Effect: Precursor to the Terahertz Kerr Effect
Δn ∝ E2
n
n = n + Δn
E
Zhong, Qin, and John T. Fourkas. "Optical Kerr Effect Spectroscopy of Simple Liquids†." The Journal of Physical Chemistry B 112.49 (2008): 15529-15539.
REGENERATIVEAMPLIFIER
(Coherent Legend)
Ti:S 800 nm1 kHz>4 mJ35 fs
fs Ti:SaOSCILLATOR
Ti:S80 MHz~ 5 nJ
B.S.85:15
DETECTIONDELAY LINE
DETECTIONPHOTODIODEλ/4
WOLLASTONPRISM
OPASignal1450 nm
400 μJ
SAMPLE
OPTICALBEAM BLOCK
= 1450 nm= 800 nm= THz
LENSPOL
DSTMS THzEMITTER
THz Kerr Effect - Experimental Setup
Allodi, Finneran, & Blake, 2015 submitted.
Heterdyne detection improves sensitivity
DETECTIONPHOTODIODESλ/ 4
WOLLASTONPRISM
SAMPLE
OPTICALBEAM BLOCK
LENSPOL
DSTMS THzEMITTER
WIRE-GRID POLARIZER
Image Credits: Rainbowphotonics.com
Allodi, Finneran, & Blake, 2015 submitted.
λ/ 2
Heterodyne-Detected THz Kerr Effect Signal!
Heterodyne-Detected THz Kerr Effect Signal!
Cuvette Response
Allodi, Finneran, & Blake, 2015 submitted.
Intramolecular Vibrational Oscillations
Oscillations in CH2I2 match perfectly the 122 cm-1 ν4 mode.
Allodi, Finneran, & Blake, 2015, submitted.
Vibrational excitation is possible at higher frequencies: CCl4
Two field interactions allow excitation above 3 THz (100 microns)
CH2I2CCl4
Cuvette material is fused silica (Suprasil)
The Optical Kerr Effect is Nonresonant
0 THz
time
7 THz
There are many overdamped intermolecular vibrations at 3 THz!
0 THz
3 THz
6 THz
time
Milestones Necessary for 2D THz Spectroscopy
✔ Generate Coherences
? Manipulate Coherences
✔ Detect Coherences
Separate pulses will differentiate the excitation process
0 THz
3 THz
6 THz
Conclusions & Future Directions
Heterodyne detection improves the sensitivity and allows phase-sensitive detection.
First nonlinear resonant terahertz vibrational coherences in a molecular liquid.
Multi-pulse schemes will reveal more information.
Acknowledgments
The Blake Group
NSF
