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Vibronic structure and photoelectron angular distribution in the photoelectron spectrum of ICN
摘要： The valence shell photoelectron spectrum of ICN has been simulated using the equation-of-motion coupled-cluster method to calculate the ionization energies and the norms of the Dyson orbitals to describe the intensity of the photoelectron bands. The simulated spectrum not only reproduces the position and intensity of the four main bands observed in the experimental photoelectron spectrum, but the vibronic structure present in the individual photoelectron bands is also reproduced to a reasonable extent. The agreement between the experimental and simulated vibronic structures at higher energies corresponding to the ?A and ?B states is particularly noteworthy. Additionally, the photoionization cross section and asymmetry parameter have been calculated for the ionization of four outermost valence molecular orbitals in the photon energy range of 0–50 eV. The computed asymmetry parameters are found to provide a qualitative description of the corresponding experimental measurements. The shape-resonance seen in the experimental asymmetry parameters and the trends seen in the calculated cross section for the four ionization channels have been explained by the partial wave analysis of the contribution of the individual angular momentum channels to the photoelectron.
关键词： ICN,photoelectron spectrum,vibronic structure,equation-of-motion coupled-cluster method,Dyson orbitals,asymmetry parameter,photoionization cross section
更新于2025-09-10 09:29:36
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Quantum interference in the femtosecond photoionization spectra of NaI molecules
摘要： This study investigates femtosecond pump–probe photoionization of NaI molecules by solving the time-dependent Schr?dinger equation?through the wave packet approach. The photoelectron spectra are presented to analyze the dynamic information of the internal wave packet. Quantum interference is observed in the photoelectron kinetic energy spectrum at a certain time delay of the probe field. The interference signals are weak but cover a wide range of energy. This finding is consistent with the interfering process of forward and returned wave packets at short internuclear distances of the repulsive potential.
关键词： photoionization,quantum interference,Wave packet dynamics,photoelectron spectrum
更新于2025-09-09 09:28:46
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Low-Energy Photoelectron Spectrum and Dissociative Photoionization of the Smallest Amides: Formamide and Acetamide
摘要： The threshold photoelectron spectrum and low-energy dissociative photoionization processes of formamide and acetamide were studied using photoelectron photoion coincidence spectroscopy and vacuum ultraviolet synchrotron radiation. Ab initio calculations and Franck–Condon simulations helped us assign the main vibrational progressions in the spectra and enabled the first conclusive assignment of the first electronically excited states. The adiabatic ionization energies to the ???+ and ???+ states of formamide (10.236 ± 0.004 eV and 10.643 ± 0.015 eV) and acetamide (9.734 ± 0.008 and 10.282 ± 0.020 eV) have been re-evaluated and spectroscopic transitions were assigned using a Franck–Condon approach. The cationic potential energy surface was explored to rationalize the observed fragmentation patterns and to construct a statistical model, which was fitted to the experimental breakdown diagram. Thermochemical thresholds were measured and calculated for H, CO, and NH2 loss from HCONH2+ as well as for CH3, NH2, CO, HCCO, and NH3 loss from CH3CONH2+. We present the first comprehensive, experimental and theoretical treatise of these fragmentation processes. The statistical model confirms fast internal conversion between the ???+ and ???+ states in formamide, as H-transfer in CO loss is shown to take place on the excited state surface. It also explains the five almost simultaneously opening dissociation channels in the acetamide cation quantitatively. The derived 0 K appearance energies have been confirmed by ab initio calculations and by comparison with state-of-the-art thermochemical data, and revise some of the previous results by more than ten times their stated uncertainty.
关键词： Dissociative Photoionization,Photoelectron Spectrum,Acetamide,Formamide,Quantum Chemistry,Spectroscopy,Molecular Structure
更新于2025-09-09 09:28:46