Vibrational distribution of Br2 molecule following photodissociation of CF2Br2 by using cavity ring down absorption spectroscopy.
Date Issued
2005
Date
2005
Author(s)
Hsu, Ching-Yi
DOI
en-US
Abstract
Cavity ring-down Spectroscopy (CRDS) is a relatively new direct absorption technique and its applications are developed very quickly in recently years. The method is based on measurement of the decay rate of a pulse light trapped in an optical cavity which is formed by a pair of highly reflective(R>99.9%) mirrors. A plot of decay rate as a function of laser frequency gives the absorption spectrum.
As for photodissociation studies of CF2Br2, the major dissociation channels are found to be
CF2Br2 → CF2Br + Br ΔH=274 kJ/mol
CF2Br2 → CF2 + Br2 ΔH=231 kJ/mol
We used a cavity ring-down spectroscopy (CRDS) to study of nascent Br2 following photodissociation of CF2Br2. The quantum yield of Br2 is found to be 0.038±0.009 following photodissociation of CF2Br2 at 248nm. According to the absorption spectrum, the nascent vibrational distribution was obtained. A comparison with the CHBr3 case reveals that nascent vibrational distribution leads to vibrationally cool. The excited parent molecules (CF2Br2) may transfer into highly vibrational levels of their electronic ground state via internal conversion. The results agree with a given theoretical calculation.
Subjects
腔體震盪吸收光譜法
二氟二溴甲烷
光分解
cavity ring down absorption spectroscopy
CF2Br2
photodissociation
Type
thesis
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