Kinetic Energy Release of the Singly and Doubly Charged Methylene Chloride Molecule: The Role of Fast Dissociation.

The center of mass kinetic energy release distribution (KERD) spectra of selected ionic fragments, formed through dissociative single and double photoionization of CH2Cl2 at photon energies around the Cl 2p edge, were extracted from the shape and width of the experimentally obtained time-of-flight (TOF) distributions. The KERD spectra exhibit either smooth profiles or structures, depending on the moiety and photon energy. In general, the heavier the ionic fragments, the lower their average KERDs are. In contrast, the light H(+) fragments are observed with kinetic energies centered around 4.5-5.5 eV, depending on the photon energy. It was observed that the change in the photon energy involves a change in the KERDs, indicating different processes or transitions taking place in the breakup process. In the particular case of double ionization with the ejection of two charged fragments, the KERDs present have characteristics compatible with the Coulombic fragmentation model. Intending to interpret the experimental data, singlet and triplet states at Cl 2p edge of the CH2Cl2 molecule, corresponding to the Cl (2p → 10a1*) and Cl (2p → 4b1*) transitions, were calculated at multiconfigurational self-consistent field (MCSCF) level and multireference configuration interaction (MRCI). These states were selected to form the spin-orbit coupling matrix elements, which after diagonalization result in a spin-orbit manifold. Minimum energy pathways for dissociation of the molecule were additionally calculated aiming to give support to the presence of the ultrafast dissociation mechanism in the molecular breakup.

[1]  W. Wolff,et al.  Strong Electronic Selectivity in the Shallow Core Excitation of the CH2Cl2 Molecule. , 2015, The journal of physical chemistry. A.

[2]  S. Montzka,et al.  Increasing concentrations of dichloromethane, CH2Cl2, inferred from CARIBIC air samples collected 1998–2012 , 2014 .

[3]  A. Rocha.  Spin-orbit splitting for inner-shell 2p states , 2014, Journal of Molecular Modeling.

[4]  W. Wolff,et al.  Outer-shell double photoionization of CH2Cl2 , 2014 .

[5]  E. C. Montenegro,et al.  Absolute cross sections for O2 dication production by electron impact. , 2013, The Journal of chemical physics.

[6]  N. Yadav,et al.  Ionic fragmentation of a CH 4 molecule induced by 10-keV electrons: Kinetic-energy-release distributions and dissociation mechanisms , 2013 .

[7]  N. Yadav,et al.  Ionic fragmentation of the CO molecule by impact of 10-keV electrons: Kinetic-energy-release distributions , 2013 .

[8]  W. Wolff,et al.  Deep core ionic photofragmentation of the CF2Cl2 molecule , 2012 .

[9]  Jean Lilensten,et al.  Doubly-charged ions in the planetary ionospheres: a review. , 2011, Physical chemistry chemical physics : PCCP.

[10]  A. Rocha,et al.  Fragmentation of the CH2Cl2 molecule by proton impact and VUV photons , 2011 .

[11]  A. C. F. Santos,et al.  Production of highly charged Ne ions by synchrotron radiation , 2011 .

[12]  J. M. Chen,et al.  State-selective enhanced production of positive ions and excited neutral fragments of gaseous CH{sub 2}Cl{sub 2} following Cl 2p core-level photoexcitation , 2010 .

[13]  Julian Hill,et al.  Determination of fecal contamination indicator sterols in an Australian water supply system , 2010, Environmental monitoring and assessment.

[14]  T. Swaminathan,et al.  Comparison of biological reactors (biofilter, biotrickling filter and modified RBC) for treating dichloromethane vapors , 2010 .

[15]  D. Céolin,et al.  Multipathway dissociation dynamics of core-excited methyl chloride probed by high resolution electron spectroscopy and Auger-electron-ion coincidences. , 2008, The Journal of chemical physics.

[16]  Lizhong Zhu,et al.  Pollution level, phase distribution and health risk of polycyclic aromatic hydrocarbons in indoor air at public places of Hangzhou, China. , 2008, Environmental pollution.

[17]  A. C. F. Santos,et al.  Fragmentation and mean kinetic energy release of the nitrogen molecule , 2007 .

[18]  D. Mathur.  Structure and dynamics of molecules in high charge states , 2004 .

[19]  P. Knowles,et al.  Spin-orbit matrix elements for internally contracted multireference configuration interaction wavefunctions , 2000 .

[20]  M. Gordon,et al.  A study of the relative importance of one and two-electron contributions to spin–orbit coupling , 2000 .

[21]  R. Grant,et al.  An experimental and computational study of the double ionization of CH3Cl, CH2Cl2, and CHCl3 molecules to singlet and triplet electronic states of their dications , 1999 .

[22]  I. Nenner,et al.  Multicoincidence mass spectrometry applied to hexamethyldisilane excited around the silicon 2p edge , 1993 .

[23]  Yang,et al.  Role of non-Coulombic potential curves in intense field dissociative ionization of diatomic molecules. , 1992, Physical review letters.

[24]  H. F. King,et al.  Theory of spin‐orbit coupling. Application to singlet–triplet interaction in the trimethylene biradical , 1985 .

[25]  Dujardin,et al.  Double photoionization of methane. , 1985, Physical review. A, General physics.

[26]  R. J. Myers,et al.  The Microwave Spectra, Structure, Dipole Moment, and Chlorine Nuclear Quadrupole Coupling Constants of Methylene Chloride , 1952 .