Slow-electron velocity-map imaging study of aniline via resonance-enhanced two-photon ionization method

Abstract

Slow electron velocity-map imaging (SEVI) of aniline has been investigated via two-color resonant-enhanced two-photo (1+1') ionization (2C-R2PI) method. A number of vibrational frequencies in the first excited state of neutral (S) and B ground electronic state of cation (D) have been accurately determined. In addition, photoelectron angular distributions (PADs) in the two-step transitions are presented and reveal a near threshold shape resonance in the ionization of aniline. The SEVI spectra taken via various S intermediate states provide the detailed vibrational structures of D state and directly deduce the accurate adiabatic ionization potential (IP) of 62,271±6cm. Ab initio calculations excellently reproduce the experimental IP value (Theo. 62,242cm). For most vibrational modes, good agreement between theoretical and experimental frequencies in the S and D states of aniline is obtained to aid us to clearly assign vibrational modes. Especially, the vibrational frequencies calculated at the CASSCF level are much better consistent with experimental data than that obtained using the TDDFT and CIS methods.

Photoelectron angular distributions from resonant two-photon ionisation of adiabatically aligned naphthalene and aniline molecules

“…The spectrum arising from the unaligned sample is consistent with the spectrum obtained by Qu and coworkers, 47 considering the differences in experimental conditions. In this figure it can be seen that the peak with maximum intensity is centered at 0.75 eV, in agreement with our expectation for the kinetic energy of photoelectrons associated with the formation of the cation in its vibrational origin; 47 the results discussed in this paper focus on these photoelectrons. The peaks at lower kinetic energies correspond to the formation of the cation in vibrationally excited states.…”

“…The ePolyScat calculations also provide values of , the coefficient of 2 (cos ) in the photoelectron angular distribution that arises following ionization of an isotropic distribution of MPAs. In the case of aniline, the trend in these values as a function of photoelectron kinetic energy can be compared with the trend in the values of the equivalent coefficient that have been determined in (1+1) two-photon ionization experiments by Qu et al 47 and by Thompson et al 48 Although the experimental values will be influenced by the small anisotropy introduced in the twophoton ionization process, in both cases the coefficient of 2 (cos ) decreases from a positive value at ~0 eV to zero at ~0.5 eV and is then increasingly negative from ~0.5 eV to ~1 eV. This comparison therefore enables us to verify the computational results and that the calculated energies are in good agreement with the experimental energies.…”

Experimental and Theoretical Investigation of the 3sp(d) Rydberg States of Fenchone by Polarized Laser Resonance‐Enhanced‐Multiphoton‐Ionization and Fourier Transform VUV Absorption Spectroscopy

“…The recorded 2D images are inverted to reconstruct the 3D velocity distributions of the photoelectrons using the pBasex method [38] and photoelectron spectra obtained from the radial velocity distributions. The electron energy scale was calibrated by recording the known S 1 origin of aniline [39] …”

Role of Triplet States in the Photodynamics of Aniline

“…In particular, the band centered at ≈3.32 eV was attributed to the 0-0 emission from T1 to S0, whereas no signature of the high-lying triplets was observed. 90,91 In order to probe the T1 decay Knee and Johnson used ultraviolet radiation to reach the ionization potential 92 of aniline at 7.72 eV and produce ions to be captured by the time-of-flight mass spectrometer. Both T1 and S1 states were ionized by the probe pulses keeping intact the hot S0 aniline molecules.…”