The HCN emission spectra with spectral resolution of 0.5 cm−1 acquired in the range of 3100–3400 cm−1 at 4 μs delay after photolysis in the presence of Ar at 2000 mTorr. The HNC emission spectra can be recognized in the range of 3450–3700 cm−1, but cannot be assigned precisely.
High-resolution spectra of (a) HCN and (b) CO as a function of the μs delay time in the photolysis of CH3COCN in the presence of Ar at 2000 and 1200 mTorr, respectively.
Time evolution of vibrational population of HCN in the v = 1 and 2 level. The data are fitted to yield production and decay rate constants for these two levels.
Emission spectra of CO from 1900 to 2200 cm−1 with spectral resolution of 0.25 cm−1 at 4 μs delay after photolysis in the presence of Ar at 1200 mTorr.
Boltzmann plot of ln N/(2J ′ + 1) versus E J /k B for CO in the v = 1, 2, and 3 levels at 4 μs delay in the presence of Ar, yielding the corresponding rotational temperature of 520 ± 30, 410 ± 20, and 400 ± 40 K, respectively. N v ,J is the relative population in the (v, J) level and E v ,J is the corresponding rotational energy.
Laser energy dependence of the HCN and CO spectral intensities within the range of 6.5–85 mJ/pulse in the presence of Ar at 1800 and 1500 mTorr, respectively. The intensity is determined by integrating the area over the low-resolution spectra of HCN and CO.
(a) The Stern-Volmer plot of the reciprocal of CH3COCN lifetime as a function of its pressure at 308 nm. (b) The Stern-Volmer plot of the reciprocal of CH3COCN lifetime as a function of Ar pressure at 308 nm. The CH3COCN pressure is fixed at 250 mTorr.
The Ar pressure dependence of low-resolution emission spectra of HCN (b) and CO (a) in the range of 2400–3200 and 1900–2300 cm−1 at 4 and 9 μs delay, respectively.
The Ar pressure dependence of the HCN area intensity over the low-resolution spectra obtained at 4 μs delay. According to Eqs. (8) and (9) in the text, the experimental data are fitted to yield the optimized rate constants for the collision-induced internal conversion.
The low-resolution spectra of HCN and HNC in the presence of Ar and O2 at the same pressure of 1200 mTorr.
(Left) The CO2 signal at 2250 nm produced in the presence of O2. (Right) Disappearance of the CO2 signal at 2250 nm in the presence of Ar.
The dissociation pathways of CH3COCN, in which the energies in kJ/mol relative to the ground state are computed with CCSD(T)/6-311+G(d,p) level of theory with B3LYP/6-311+G(d,p) zero-point energy corrections at B3LYP/6-311+G(d,p) optimized geometries. For those pathways with dashed line, the attempts for locating the transition states are not made or not successful.
(a) The structures of reactant and products and (b) the structures of several transition states.
RRKM rate constants computed with B3LYP/6-311+G(d,p) zero-point energy corrected CCSD(T)/6-311+G(d,p) energies and B3LYP/6-311+G(d,p) harmonic frequencies for reactions paths on the adiabatic singlet ground state surface of CH3COCN at 308 nm.
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