Relaxation of Vibrationally Excited Trifluorobenzene and Tetrafluorobenzene by Collisions with Carbon Dioxide

• Main Author: Johnson, Alan M.
• Format: Others
• Published: BYU ScholarsArchive 2009
• Subjects: Trifluorobenzene; Tetrafluorobenzene; Energy Transfer Probability Distribution Function; collisional energy transfer; Biochemistry; Chemistry
• Online Access: https://scholarsarchive.byu.edu/etd/2177; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=3176&context=etd

An investigation into the relaxation of highly vibrationally excited trifluorobenzene and tetrafluorobenzene following collisions with carbon dioxide was performed using diode laser transient absorption spectroscopy. A 248 nm excimer laser prepared the vibrationally hot (E'~41,000 cm-1) fluorobenzene molecules. Large amounts of translational and rotational energy are transferred through collisions between the hot donor molecule and CO2. Rate constants and collisional probabilities were calculated by probing the high J states (J=58~80) of CO2 in the vibrational ground state, 0000, with measurements taken 1 µsec, ¼ the mean gas collision time, following each excimer laser pulse. The energy transfer probability distribution function, P(E,E'), was calculated for each molecule using the state-resolved probabilities and the energy gain of the bath. The study found a relationship between the fraction of strong collisions and the donor's dipole moment. Additionally, these findings support an application of Fermi's Golden rule to collisional energy transfer by linking the shape of P(E,E') to the shape of the donor's density of states as a function of ΔE.