Vibrationally excited populations from IR-multiphoton absorption. II. Infrared fluorescence measurements

Abstract

Infrared emission spectra were obtained for 1, 1, 2-trifluorethane (TFE) excited by infrared multiphoton absorption (1079.85 cm−1). The emission features show that the HF reaction product is formed in vibrational states up to about v=3. Furthermore, emission attributed to F–C≡C–H was observed near 3320 cm−1, indicating that the difluoroethylene primary products of TFE decomposition undergo secondary photolysis; since the difluoroethylene products at room temperature do not absorb laser light, they must be formed vibrationally excited. The emission from the C–H stretch modes of TFE was readily identified near 2980 cm−1 and the emission intensity was obtained as a function of laser fluence. These data are in excellent agreement with predictions based on the theoretical expression for fluorescence intensity and the reconstructed populations determined by the Master Equation calculations described in the preceding paper. These results provide additional support for the accuracy of the reconstructed population distributions and for the theory relating infrared fluorescence intensity to total vibrational energy in polyatomic molecules.

Energy Flow and Bond Dissociation of Vibrationally Excited Toluene in Collisions with N2and O2

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Molecules highly excited to near their dissociation threshold can undergo bond dissociation and vibrational relaxation, processes that play an important role in reaction dynamics. Most of experimental studies have been carried out using time-resolved infrared flourescence (TR-IRF) [2][3][4] or ultraviolet absorption (UVA). [5][6][7][8] Several studies have been employed by techniques based on photothermal processes.…”

Energy transfer of highly vibrationally excited molecules studied by crossed molecular beam/time-sliced velocity map ion imaging

“…Infrared fluorescence was used by Barker and co-workers to measure the energy transfer of hot molecules [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. In these experiments, the decay of hot molecule's internal energy due to collisional energy transfer to the bath molecules was monitored by infrared fluorescence emitted from hot molecules as a function of time.…”

A direct comparison of vibrational deactivation of hexafluorobenzene excited by infrared multiple photon absorption and internal conversion

“…Various workers have either calculated this distribution [3][4][5][6] or it has been inferred using experimental techniques such as Raman spectroscopy. 31,32 Problems arise as the distribution can be bimodal, resulting from a near thermal population of those molecules that did not absorb, and a higher energy distribution of molecules that absorbed many photons.…”

“…This arises because there is uncertainty in the initial energy distribution associated with the IRMPA process. [3][4][5][6] Nevertheless, it has been shown theoretically that under appropriate conditions the results extracted from the data depend solely on the average excitation energy, i.e., they are independent of the initial distribution. 10,11 The average internal energy the excited molecule initially reaches after IRMPA is controlled by varying the fluence of the excitation laser.…”

“…[2][3][4][5][6][7][8][9] In contrast with studies utilizing UV pumping followed by IC, IRMPA remains a poor cousin. This arises because there is uncertainty in the initial energy distribution associated with the IRMPA process.…”