Photochemistry of (FCO)2 at 266 nm. UV and IR Emission.

BURGOS PACI, MAXI A.; LUCÍA LANFRI; MATIAS BERASATEGUI; ANGEL ANZANI

Simposio; 25 th International Symposium on Gas Kinetics; 2018

Introduction. Oxalylfluoride has an allowed electronic Â1 Au ← X1 Ag transition with an absorption band located at about 308 nm.1,2 For excitation energies above this wavelength the fluorescence efficiency decreases, and the photochemical decomposition takes place.3,4 In the present work we explore the dynamics of fluorescence and photodisociation resolved in time, in the presence of different quenchers.Experimental. The photolysis was initiated with a Ne: YAG at his fourth harmonic (266 nm, 0,400 W). The (FCO)2 absorption cross-section at this wavelength is ≈ 1 × 10-19 cm2 molecule-1.4 The IR radiation was collected with a concave golden mirror and focused through a filter (2000 ? 2400 cm-1) to an InSb detector. To register the UV-Visible phosphorescence a monochromator connected to a photomultiplier was used (resolution of 0.1 nm). For the spectroscopic measurement, a FTIR and a fluorometer were used.Results. Under the experimental conditions, several processes may occur:(CFO)2* → (CFO)2 + hν(UV-Vis)(CFO)2* → 2 FCO* → F + CO*(CFO)2* → CO* + CF2OCO* → CO + hν(IR)The phosphorescence spectrum is presented in Figure 1.a. We follow the band at 356.7 nm to register the temporal decay of the â3Au. In the presence of inert gases (O2 and Ar) only a decrease in life-time was observed, whereas in the presence of more complex molecules an increase in the total emission takes place with the increase in pressure (the test was carried out with gases such as CO, CH3C≡N and cyclohexane). Figure 1.b. presents the time-resolved fluorescence for the band at 356.7 nm at different pressures of (CFO)2.Figure 1.c. presents the FTIR spectrum of the final product of the photolysis. With the IR filter, only the CO* (vibrational excited) emissions region is measured. Figure 1.d. presents the time-dependence of the IR emission bands. No pressure dependence was observed when an inert gas is loaded, but the IR signal decrees drastically with the increase of complex molecules pressure.Conclusion. Complex molecules could determine the phosphorescence or rupture yield once the (CFO)2 molecule is excited by laser radiation at 266 nm. This effect is due to the collisional relaxation suffered by the (CFO)2*.p { margin-bottom: 0.25cm; direction: ltr; color: rgb(0, 0, 10); line-height: 115%; text-align: left; }p.western { font-family: "Calibri", serif; font-size: 11pt; }p.cjk { font-family: "WenQuanYi Zen Hei Sharp"; font-size: 11pt; }p.ctl { font-family: "Calibri"; font-size: 11pt; }a:link { }Bibliography.[1] V.I. Makarov, I.V. Khmelinskii. Chem. Phys. 321 (2006) 233.[2] A.P. Baronavski, J. R. McDonald. Chem. Phys. 67 (1977) 4286.[3] C.W. Bock, Y.N. Panchenko, S.V. Krasnoshchiokov. Chem. Phys. 147 (1990) 65.[4] C.J. Cobos, A.E. Croce, E. Castellano. Chem. Phys. Letters. 239 (1995) 320-325.