A typical depletion curve, representing methyl radical signal as a function of irradiation time, which is used to correct individual rotational scans for the loss of signal as a result of the surface photoreaction. Open circles denote experimental data while the solid curve represents a four parameter, biexponential fit to the data. Such complex depletion kinetics are commonly observed for substrate-mediated photochemistry on TiO2 surfaces.
Rotationally resolved REMPI spectrum of 0.15 eV methyl radicals via the transition of the 4pz Rydberg state. The top trace is the experimental data and the bottom trace is a PGOPHER simulation at TR = 325 ± 25 K which has been vertically offset for clarity.
(2 + 1) REMPI spectrum (2A2″(3pz) ←← ) of methyl radicals of the fast channel. The spectrum shows little vibrational excitation for radicals in this channel. Data were recorded using a 21 μs laser delay and a 3 cm−1 step size and are not corrected for variations in ionization laser intensity.
Vibrationally resolved depletion curves for methyl radicals of the fast channel. Both datasets have been corrected for differences in ionization laser power and the ν = 1 set has been multiplied by 20 for ease of comparison. For both measurements, the prepared sample was irradiated using a photon flux of ∼2.3 × 1012 photons cm−2 s−1.
(a) Energy distribution for methyl radicals in the ν2 (ν = 0) vibrational state and (b) in the ν2 (ν = 1). The experimental data are shown as open circles, whereas dashed curves represent fits for the individual kinetic energy components. The solid curve represents the sum of these two fits.
Combined fits as a function of vibrational state. Curves are vertically offset for clarity and the mean fast-channel energies are marked for comparison purposes.
Values showing the mean energies for energy distributions taken for each vibrational state. Also shown are the ratios showing the relative population of methyl radicals in the fast and slow channels. Energy values are in units of eV and are accurate to within ∼6% of the quoted value.
Article metrics loading...
Full text loading...