The photodissociation dynamics of CH3I from 277 to 304 nm is studied with our mini-TOF photofragment translational spectrometer. A single laser beam is used for both photodissociation of CH3I and REMPI detection of iodine. Many resolved peaks in each photofragment translational spectrum reveal the vibrational states of the CH3 fragment. There are some extra peaks showing the existence of the hot-band states of CH3I. After careful simulation with consideration of the hot-band effect, the distribution of vibrational states of the CH3 fragment is determined. The fraction σ of photofragments produced from the hot-band CH3I varies from 0.07 at 277.38 nm to 0.40 at 304.02 nm in the I* channel and from 0.05 at 277.87 nm to 0.16 at 304.67 nm in the I channel. Eint/Eavl of photofragments from ground-state CH3I remains at about 0.03 in the I* channel for all four wavelengths, but Eint/Eavl decreases from 0.09 at 277.87 nm to 0.06 at 304.67 nm in the I channel. From the ground-state CH3I, the quantum yield Φ(I*) is determined to be 0.59 at 277 nm and 0.05 at 304 nm. The curve-crossing probability Pcc from the hot-band CH3I is lower than that from the ground-state CH3I. The potential energy at the curve-crossing point is determined to be 32 740 cm−1.

The photodissociation of CF3I has been studied near 304 nm. The partially resolved vibrational peaks in the I* and I channels reveal that the ν2 umbrella mode of CF3 is preferentially excited. Besides, in the I* channel, the extra vibrational peaks assigned to the umbrella mode of CF3 from the hot band ν3′=1,2 states of CF3I are also partially resolved. The Eint/Eavl shows a gradual increase as the state of CF3I changes from ν3′=0 to ν3′=2. The anisotropy parameter is also obtained and discussed with the interrelation of the 3Q1, 3Q0, and 1Q1 potential energy surfaces.Resolved photofragment translational spectra of the I* channel from CF3I photodissociation at 304.02 nm.

The band origin of the S1 ← S0 transition of p-methylstyrene is determined to be 34,276 cm−1 by one color resonant two photon ionization (1C-R2PI) method, which is red shifted by 3811 cm−1 with respect to that of benzene. This indicates that the interaction of the methyl and vinyl groups with the ring in the S1 state is greater than that in the S0 state. The active vibrations assigned from the R2PI spectrum are found to be the in-plane ring modes. The bands at 399, 613, 724, and 786 cm−1 are assigned to the vibrations 9b, 6b, 12, and 1, respectively, and discussed in detail. The experimental results are well supported by ab initio and density functional theory (DFT) calculations.

The photodissociation of ethyl iodide at 279.71, 281.73, 304.02 and 304.67 nm has been studied on our new mini-photofragment translational spectrometer with a total flight path of only 5 cm. Some vibrational peaks are firstly resolved in the TOF spectra of I*(2P1/2) and I(2P3/2) channels. These vibrational peaks are assigned to the excitation states (v2 = 0, 1, 2, …) of the umbrella mode (v2, 540 cm−1) of the photofragment C2H5, and the distribution of the vibrational states is obtained. The dissociation energy has been determined to be D0(C-I)=2.314 ± 0.03 eV. The energy partitioning of the available energy (Eavl=ET+Eint=ET+EV,R) calculated from our experimental data Ēint / Eavl = 22.1% at 281.73 nm, 22.4% at 304.02 nm for the I* channel, and Ēint / Eavl = 25.2% at 279.71 nm, 25.9% at 304.67 nm for the I channel, seem to be more reliable.