Electronic excitations of CH2Cl2 studied by fast electron scattering

• Published in: Journal of quantitative spectroscopy & radiative transfer 2022-09, Vol.287, Article 108227
• Main Authors: Nie, Zhi-Wei, Wang, Shu-Xing, Ma, Kun, Wang, Li-Han, Xu, Yuan-Chen, Du, Xiao-Jiao, Zhu, Lin-Fan
• Format: Article
• Language: English
• Subjects: BE-scaling; Cross section; Dichloromethane; Electron scattering; Oscillator strength
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/j.jqsrt.2022.108227

•Generalized oscillator strengths of the electronically excited states ranging from 5.8 eV to the first ionization threshold for dichloromethane (CH2Cl2) have been determined by fast electron scattering.•Detailed analysis is made for the transition assignments in the measured energy-loss range of 5.80–11.32 eV.•Optical oscillator strengths are obtained by extrapolating the measured generalized oscillator strengths to its limit at zero momentum transfer.•Integral cross sections from the excitation threshold to an extended impact energy of several keV are derived from the measured data utilizing the BE-scaling method. Fast electron has been applied to probe the electronic excitations of dichloromethane by employing an angle-resolved electron-energy-loss spectrometer. The measurements were carried out with an incident electron energy of 1500 eV and an energy resolution of about 70 meV. Generalized oscillator strengths of the electronically excited states ranging from 5.8 eV to the first ionization potential have been determined at an absolute scale by applying the crossed-beam based relative flow technique. The measured data are fitted with the well-known Lassettre formula as power series, in which the intercepts come up to the optical oscillator strengths for the corresponding dipole-allowed transitions. The expansion also enables the integration of the generalized oscillator strengths over the whole momentum transfer region to obtain the Born cross sections. The scaled integral cross sections with a satisfactory accuracy are thus available by introducing the BE-scaling method. The comprehensive data sets can deepen our understanding on the electron impact excitation of dichloromethane on the one hand and supplement the molecular database for modelers on the other hand.