Four-temperature kinetic model for CO2 vibrational relaxation

2021 ◽  
Vol 33 (1) ◽  
pp. 016103
Author(s):  
A. Kosareva ◽  
O. Kunova ◽  
E. Kustova ◽  
E. Nagnibeda
Keyword(s):  
Kinetic Model ◽  
Vibrational Relaxation

scholarly journals Anomalous Humidity Dependence in Photoacoustic Spectroscopy of CO Explained by Kinetic Cooling

2020 ◽  
Vol 10 (3) ◽  
pp. 843 ◽  
Author(s):  
Jakob Hayden ◽  
Bettina Baumgartner ◽  
Bernhard Lendl
Keyword(s):  
Kinetic Model ◽  
Vibrational Relaxation ◽  
Photoacoustic Signal ◽  
Collisional Relaxation ◽  
Vibrational Resonance ◽  
Experimental Conditions ◽  
Gas Phase Molecules ◽  
Detailed Kinetic Model ◽  
Humidity Dependence ◽  
Water Contents

Water affects the amplitude of photoacoustic signals from many gas phase molecules. In quartz-enhanced photoacoustic (QEPAS) measurements of CO excited at the fundamental vibrational resonance of CO, the photoacoustic signal decreases with increasing humidity, reaches a pronounced minimum at ~0.19%V, and increases with humidity for higher water contents. This peculiar trend is explained by competing endothermal and exothermal pathways of the vibrational relaxation of CO in N2 and H2O. Near-resonant vibrational–vibrational transfer from CO to N2, whose vibrational frequency is 188 cm−1 higher than in CO, consumes thermal energy, yielding a kinetic cooling effect. In contrast, vibrational relaxation via H2O is fast and exothermal, and hence counteracts kinetic cooling, explaining the observed trend. A detailed kinetic model for collisional relaxation of CO in N2 and H2O is presented. Simulations using rate constants obtained from literature were performed and compared to humidity dependent QEPAS experiments at varying pressure. Agreement between the experiments and simulations confirmed the validity of the model. The kinetic model can be used to identify optimized experimental conditions for sensing CO and can be readily adapted to include further collision partners.

Double-Excitation Dynamics in m-LPPP probed with sub-20 fs Time Resolution

2003 ◽  
Vol 771 ◽  
Author(s):  
C. Gadermaier ◽  
G. Cerullo ◽  
C. Manzoni ◽  
U. Scherf ◽  
E.J.W. List ◽  
...  
Keyword(s):  
Vibrational Relaxation ◽  
Broad Band ◽  
Generation Efficiency ◽  
Exciton Dissociation ◽  
Charge Generation ◽  
Carrier Generation ◽  
Dissociation Probability ◽  
Ultrafast Relaxation ◽  
First Excited State ◽  
Differential Transmission

AbstractIn a novel modification of transient differential transmission spectroscopy, the first excited state S1 is reexcited via a second laser pulse towards a higher lying state Sn. The dynamics of the relaxation of this state Sn as well as the states created from Sn are revealed by a broad-band probe pulse.We find that the charge carrier generation efficiency from Sn is higher compared to S1. The push and probe durations below 20 fs enable the temporal resolution of the ultrafast relaxation of the Sn state and enables us to identify the two main contributions to enhanced charge generation from Sn, energy migration towards sites of high dissociation probability, and exciton dissociation during vibrational relaxation.

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