A new class of Norrish type I processes: .alpha.-bond cleavage upon 1(n,.pi.*(C = O)) excitation in the acid halides

Determination of Absolute Product Branching Ratios in Mass Spectrometric Experiments: Detecting Acetyl Radicals at CH2CO+

“…translational energy distribution, P(E T ) shown in Figure 2. This P(E T ) is identical to that reported by North et al 7 and very similar to that of Person et al 6 Figure 3 shows the photofragment TOF signal at m/e + ) 42 (CH 2 CO + ) after 1 500 000 laser shots. This is the daughter ion of the acetyl radical fragment which is momentum matched to the Cl atom detected in the 35 Cl + spectrum in Figure 1.…”

“…Acetyl Chloride: Detection Efficiency Calibration. We only briefly present dissociation data as it pertains to branching ratio determination; for details on the photodissociation dynamics of acetyl chloride at 248 nm see Person et al 6 and North et al 7 Figure 1 shows the photofragment time-of-flight (TOF) spectrum taken at m/e + ) 35 (Cl + ) after 300 000 laser shots resulting from primary C-Cl bond fission after 1 [n(O), π*(CdO)] excitation at 248 nm. Forward convolution fitting of this spectrum gives the center-of-mass (c.m.)…”

Determination of the Barrier Height for Acetyl Radical Dissociation from Acetyl Chloride Photodissociation at 235 nm Using Velocity Map Imaging

“…The acetyl radicals were ionized with a 157 nm beam generated from a GAM (EX10F/ 300) F 2 laser which was fired 40 ns after the photolysis laser. RRKM calculations indicate that CH 3 CO radicals with energy 0.1 kcal/mol above the barrier have a lifetime of ≈5 × 10 -10 s. 8 As predicted by the short lifetime of the radical, the magnitude of this delay was found to have negligible effect on the radical signal when varied between 10 and 400 ns. The path of the 157 nm beam was evacuated to minimize the absorption by O 2 and N 2 en route to the high vacuum chamber.…”

Photodissociation Dynamics

“…In CX 3 I (X ) H, D, F) 174 and ICN, [175][176][177] if one photoexcites molecules with one or more quanta in the bend, the dissociative trajectories traverse the conical intersection at bent geometries where the splitting between adiabats is larger, resulting in an increase in the branching to the adiabatic reaction products. A somewhat different example of the sensitivity of nonadiabatic effects to the region the surface accessed by the molecular wave function occurs in the photodissociation of HCO.…”