The Photoelectron Imaging Of NH₃ Molecule

Exploring the microcosmic level structure and ionization dynamics of molecular have been draw more attention.In the process of photoionization,molecule could be ionized,exciting from the bound state to the continuous state,when its electron absorb enough photons under the interaction with laser.The excited photoelectron could carry the information of it under the bound state and the excited photoelectron from different ionization orbital could carry the information of orbital,so exploring the photoelectron energy and electron orbital space information can effectively acquire the information of molecular bound state,the microscopic structure and ionization dynamics.Photoelectron velocity imaging technology is an effective method to detect average kinetic energy and angular distribution of photoelectron.This method can obtain the physical information of the photoelectron in ionized state indirectly,and obtain the structure information of molecular bound state.In the process of multiphoton ionization,the photoelectron angular distribution has a close relationship with the excited state electronic distribution.Resonance enhanced multiphoton ionization?REMPI?is a powerful tool for analyzing small molecules or molecules which do not have fluorescence radiation in the firing process.So,we studied ammonia molecules using resonant enhanced multiphoton ionization technology and photoelectron imaging technology.In this work,we mainly studied the NH₃ molecular photoelectron imaging with the change of laser intensity.By observing the changing rule of the photoelectron imaging under different laser intensity,the molecule resonant enhanced multiphoton ionization channel switching and angular distribution of NH₃ were analyzed.We explored photoelectron imaging of NH₃ molecule under the condition of laser wavelength at 800 nm and 400 nm,respectively.The channel switching were found at 800 nm and 400 nm with the changing of laser intensity.The kinetic energy spectrum and angular distribution were obtained through the anti-abel transformation of the original image,and then the ionization channel was confirmed successfully.Under the condition of the laser wavelength of 800 nm,kinetic energy peak are located at: 0.99 e V,0.33 e V and 0.75 e V.In the process of excitation process,the intermediate resonance state are?6+2?,?6+2?and?7+2?,respectively.In angular distribution,we present the angular distribution of different kinetic energy peak.Through analyzing the angular distribution of kinetic energy peak,we found that different kinetic energy peak has different angular distribution,and confirmed that every electronic state has its own angular distribution.At the same time,after contrasting the same kinetic energy peaks in the condition of angular distribution under different laser intensity,we found that the kinetic energy peak has the same angular distribution under different laser intensity.Under the condition of the laser wavelength of 400 nm,resonance enhanced multiphoton ionization process is?2 + 2?,the intermediate state of two-photon inspiring process is state and the vibration mode is = 3.Kinetic energy peak are located at: 0.86 e V,1.16 e V and 1.6 e V.Since the REMPI process shares the same initial and intermediate states but different ionic levels,We have assigned the three major peaks as 1223,1123 and 1023.We analysized the information of angular distribution at 400 nm,and obtained the result that different continuous state ionization peak has different angular distribution.