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Chuanxi Duan (段传喜) Central China Normal University Wuhan, China
71th Meeting - June 20-24, 2016 Champaign-Urbana, Illinois Vibration-rotation-tunneling spectrum of formic acid dimer in the 7.3 μm region Chuanxi Duan (段传喜) Central China Normal University Wuhan, China
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Outline Previous high resolution studies Experimental method
Results and analysis HCOOH-HCOOH HCOOD-HCOOH HCOOD-HCOOD Conclusions
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Formic acid dimer: a prototype for double hydrogen-bond and proton transfer
Key questions: Mode-specific tunneling splitting The isotope effect J. Chem. Phys. 117, 7162 (2002)
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Previous high resolution studies on formic acid dimer
Özgür Birer and Martina Havenith, Annu. Rev. Phys. Chem. 60, 263 (2009)
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The Fermi-triad system of (HCOOH)2 in the C-O stretching region, lead-salt laser diodes
J. Chem. Phys. 140, (2014) ISMS 2014, RD07
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Can we find a less-perturbed IR band for (HCOOH)2 ?
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Experimental setup DFB-QCL Astigmatic multi-pass cell to pump IR
Laser controller IR P Nozzle Valve Reference gas cell NI-DAQ Detector ulse generator Etalon Gas supply Wavemeter Experimental setup DFB-QCL Astigmatic multi-pass cell
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Multi-step Rapid-scan with DFB-QCL
Successively moving pulsed jet ~1.5 ms Reference gas Passive frequency locking Merged jet spectrum 10 × 1.0 ms
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Supersonic jet: HCOOH/ Ar, DFB-QCL
HCOOH-HCOOH, C-H bending fundamental Observed Simulated
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HCOOH-HCOOH observed simulated
Close to the band origin: observed and simulated spectrum are in good agreement.
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HCOOH-HCOOH observed simulated by PGOPHER
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Energy crossing between two tunneling components: J ~ 12.5
Ground state, Ka = 0 Energy crossing between two tunneling components: J ~ 12.5
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Ground vibrational state, Ka = 1
Energy crossing between two tunneling components: J ~ 12.5, 13.5
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Excited vibrational state, Ka = 0
Energy crossing between two tunneling components: J ~ 17.5
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Rotation-tunneling coupling (c-type Coriolis interaction)
Observed Simulated Fit and simulated by PGOPHER
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HCOOH/D2O mixtures, Ar buffer gas
DFB-QCL
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H-O-C-H bending fundamental
HCOOH-HCOOD H-O-C-H bending fundamental H Observed D Simulated
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D-O-C-H bending fundamental
HCOOD-HCOOD D-O-C-H bending fundamental D Observed D Simulated
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Observed linewiths (FWHM) for HCOOH-HCOOD, HCOOH and HCOOD-HCOOD
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HCOOH-HCOOH DCOOH-DCOOH HCOOH-HCOOD HCOOD-HCOOD DCOOD-DCOOD Ground state 0.0165(2) 0.0125(3) < < < 0.002 C-O stretching 0.0115(3) 0.0031(3) C-H bending 0.0045(1) J. Chem. Phys. 140, (2014), and this work Annu. Rev. Phys. Chem. 60, 263 (2009)
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Conclusions A multi-step rapid-scan method for pulsed jet IR spectroscopy based on DFB-QCL is developed. The C-H bending fundamental bands are measured and analyzed for HCOOH-HCOOH, HCOOD-HCOOH, and HCOOD-HCOOD. Strong rotation-tunneling coupling in HCOOH-HCOOH is identified.
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Acknowledgement Wei LUO (left) Yuluan ZHANG (middle)
Zhuang LIU (right) Prof. Fengqi LIU and Lijun WANG Institute of Semiconductor Chinese Academy of Sciences
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