Three-Body Fragmentation from Single Ionization of Water by Electron

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Three-Body Fragmentation From Single Ionization of Water by Electron Impact: The Role of Satellite States Natalia Ferreira, Lucas Sigaud, and Eduardo Chaves Montenegro J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.7b01986 • Publication Date (Web): 14 Apr 2017 Downloaded from http://pubs.acs.org on April 18, 2017

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The Journal of Physical Chemistry

Three-body Fragmentation from Single Ionization of Water by Electron Impact: the Role of Satellite States Natalia Ferreira,∗,† L. Sigaud,∗,‡ and E. C. Montenegro∗,¶ †Centro Federal de Educa¸cão Tecnológica Celso Suckow da Fonseca (CEFET-RJ), 20271-110, Rio de Janeiro, RJ, Brazil ‡Universidade Federal Fluminense (UFF), 24210-346, Niteroi, RJ, Brazil ¶Universidade Federal do Rio de Janeiro(UFRJ), 21941-972, Rio de Janeiro, RJ, Brazil E-mail: [email protected]; [email protected]; [email protected]

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Abstract Ionization of water with energy transfers close to the 2a1 inner valence orbital is accompanied by a fast electronic rearrangement driven by electron relaxation and electron-electron correlations. Quasi-degenerate single vacancy and satellites one-electron-two-vacancies excited states in outer shells are created and leave their fingerprints in the three-body fragmentation pattern. Single vacancy states have been associated to Auger decay and double ionization. Satellites excited states are here convincingly assigned to single ionization. We focus on the H0 + O+ + H0 fragmentation by electron impact taking advantage of the high sensitivity of the Delayed Extraction Time-Of-Flight (DETOF) technique to uncover kinematic attributes of supra-thermal O+ ions. It is found that the H0 ejections occur under a large angular rearrangement, in an approximate linear geometry, and leaving the O+ near at rest, with ∼ 50% of the O+ produced in water fragmentation by swift electrons presenting this feature.

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Introduction

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For three or many-body fragmentation, some of these observables are not directly available from pump-probe experiments. Specifically designed set-ups are required to directly access them in order to give a more comprehensive picture of the molecular dynamics behind fragmentation. Theoretical support to interpret the experiment, if needed, is also more cumbersome since simpler potential energy curves must be replaced by potential energy surfaces. Indeed, even in the case where a triatomic molecule fragments into two moieties, elaborate modeling might be needed since all three bodies can actively participate in the vibronic coupling leading to fragmentation, as shown by Suarez et al. 14 in determining the branching ratios of channels H2 O+ → OH+ + H and H2 O+ → OH + H+ . When ionizing radiation falls upon the water molecule, the molecular ion can remain stable or fragment into two or three bodies. The observed final pattern depends on the amount of energy deposited and is directly associated with the production of vacancies in the molecular orbitals of water, whose electronic configuration in the ground state is (1a1 )2 (2a1 )2 (1b2 )2 (3a1 )2 (1b1 )2 . Three-body decay occurs preferentially if an electron is removed either from the core orbital, 1a1 , or from the innermost valence orbital, 2a1 . A vacancy produced in the 2a1 molecular orbital causes a fast relaxation of all valence electrons, changes the correlation energy of all electron pairs, and induces a relative movement among the nuclei within the same time scale. 15,16 As a consequence, both the independent particle approximation and the BornOppenheimer approximation break down. 17,18 In this fast electronic rearrangement phase, the single 2a1 vacancy state is mixed with satellites (or shake-up) one-electron-two-vacancies excited states in outer shells, which are responsible for the broadband observed in the photoelectron and e-2e spectrum of water in the 2840 eV region around the 2a1 vertical ionization energy of 32.3 eV. 15,16,19–21 The elucidation of the mechanisms behind the fragmentation following this electronic rearrangement leads to the question of if there are any signatures in the three-body decay that can disentangle this

Water fragmentation products are booster radicals in post-collisional chemistry of water-based environments submitted to radiation. Its importance is well recognized and studied in environments as diverse as radiobiology, 1 radiation therapy 2 or planetary atmospheres and magnetospheres. 3,4 The production of H2 O+ , H+ , OH+ and O+ by photons, 5 electrons 6 or protons 7,8 is known and used as input data for the simulation of radiolysis 9 or radiation damage. 10 On the other hand, both the conceptual description of the fragmentation process and the kinematic characterization of the products are much less known. The latter is needed, for example, in post-collisional charge exchange reactions, like O+ +H2 O → H2 O+ + O, due to its sensitivity to the relative velocity between O+ and H2 O, a prevailing characteristic of these kind of reactions. From the experimental point of view, there are few available methods capable of obtaining the kinematic characterization of sub-thermal ionic fragments in the center of mass system, especially if it is the only ion produced, with the other products being neutral. From the conceptual point of view, the difficulty to obtain a description of the temporal evolution of the relaxation and fragmentation of the molecule, after the initial vacancy is produced, appears because some of these products originate from vacancies created in the inner valence shells. Electronic rearrangement following inner valence shell vacancies is strongly governed by electron correlations. Electron correlations play a key role in the relaxation of atoms, molecules and clusters through mechanisms such as Auger decay, interatomic decay, or charge migration. 11,12 These relaxation mechanisms are very fast 11,12 and several of their features in various systems have been investigated in the last years through pump-probe experiments. 11,13 This fast electronic rearrangement ultimately affects the nuclear motion and the fragmentation pattern, as well as the internal state, the translational energy and angular distributions, the branching ratios and the charge state of the final fragments.


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tron beam pulse and the extraction pulse. 29–31 Absolute cross sections for entangled fragments in the mass spectra 29,32 or mixed fragmentation channels involving different neutral species 33 have been recently obtained using this technique, which is particularly sensitive to slow fragments. The experiment was performed at UFRJ with a 50 ns pulsed electron beam with a repetition rate of 2x104 Hz and for energies within the 30-700 eV range. The electron gun is coupled to a gas cell kept at 2x10−4 Torr and to a Faraday cup. 31 The recoil ions are guided through a double focusing time-of-flight mass spectrometer by a pulsed electrostatic electric field of approximately 21 kV m−1 and a rising time of the order of 100 ns and are detected by a micro-channel plate detector. The quality of the fit to the data set was indicated by the coefficient of determination, R-squared (R2 ). 34 For all impact energies, the curve adjusting the experimental data for different delay times had always a R2 > 0.99, and their uncertainties were established using the criteria of keeping R2 > 0.97. The DETOF methodology transforms to the time delay space the set of translational kinetic energy distributions better able to adjust the dependence, with the increasing delay, of the variation of the normalized number of counts of a specific peak in the mass spectrum. The result of this analysis indicates the same pattern for the O+ fragment for all impact energies above the vertical ionization energy of the 2a1 orbital. On the other hand, for an impact energy of 30 eV, a single distribution is sufficient to fit the experimental data. By adjusting their relative weights, the data for all other measured impact energies can be fitted by just three distributions. This procedure and results are shown in Fig. 1 for 30 eV and 450 eV impact energies. Panels (c) and (d) show the constituent distributions as a function of the kinetic energy of the O+ ions, and in panels (a) and (b) these same distributions are represented in the time delay space along with the experimental data. According to the R2 criterion mentioned above, the average kinetic energies associated to three distributions indicated in Fig.1 are 0.063 ± 0.010 eV (Expo), 0.20 ±

configuration mixing. Single vacancies produced in core orbitals have the Auger decay as their main route of relaxation and identification. In contrast, the possibility of Auger decay of single vacancies in the inner valence orbitals is not so obvious and it can be questioned if an analysis based on the independent particle approximation indicates their blocking due to energy conservation. Although unclear on the theoretical side, experimental evidence of the Auger mechanism in the decay of the 2a1 water orbital was obtained a decade ago. 22 Auger and two-step (TS1 and TS2) 23 contributions to double ionization were separated due to the different signatures that these two contributions impart in the dependence, with the projectile energy, of cross sections for the two and three body fragmentation, OH+ + H+ and O+ + H+ + H0 . 22,24–26 The shake-up three-body fragmentation counterpart associated to 2a1 vacancy in water is a quite open and unexplored issue. Among the valence molecular orbitals, the O+ fragment is considered to come only from vacancies in the 2a1 . 25,27 It has an appearance energy below 32.3 eV and, in this low energy region, their production is associated purely to single ionization. 28 In this paper we show that this fragmentation branch has a clear kinematic fingerprint. We use electron impact ionization together with the Delayed Extraction TimeOf-Flight (DETOF) technique to uncover kinematic and dynamic features impinged to the O+ recoil ion associated to single ionization and which are markedly different from those associated with the Auger decay. Furthermore, we show that the satellite decay is accompanied by a large angular bond rearrangement, occurring in the linear geometry of the molecular ion.

Experiment DETOF is an energy-resolved technique that gives the kinetic energy distribution of each recoil ion by selecting the velocities that are directed to the time-of-flight tube through a gradual increase of the delay time between the elec-


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energy distribution of the O+ ions features two distinct regions, associated to the different ways of how fragmentation correlates the rapid rearrangement of electrons and nuclei. The exponential distribution obtained at 30 eV impact energy, and below the vertical 2a1 ionization energy, retains the same shape up to our higher measured impact energy, 700 eV, and correlates quite well with single ionization coincidence experiments, as shown in panel (a) of Fig. 2. These dynamic and kinematic fingerprints - the appearance energy and the independence of the shape of the kinetic energy distribution with the impact energy - are strong indications that the shake-up process dominates the single ionization of water, releasing H0 + O+ + H0 for all impact energies. The exponential distribution is a representation of a set of low-energy (thermal and suprathermal) O+ ions and was found to be quite sharp, with an average kinetic energy of 0.063 eV. Meanwhile, O+ ions produced with kinetic energies above ∼ 0.063 eV are described by the two Gaussians centered at 0.2 and 1.2 eV and, according to the results displayed in panel (b) of Fig. 2, are associated to double ionization, releasing H0 + O+ + H+ . This separation between single and double ionization into two well defined regions of translational kinetic energies is related to the bond rearrangement, as will be discussed later. Double ionization has its appearance energy at ∼ 36.9 eV 16 and is due to two mechanisms: direct double ionization and Auger decay of a single vacancy in orbital 2a1 . 24–26 The maximum direct double ionization occurs at ∼ 250 eV with the Auger decay dominating at high energies. 24–26 The narrow supra-thermal range found for the shake-up process indicates that the ejection of two neutral Hydrogens follows a threebody concerted decay, since a wider distribution would be expected for a sequential decay. 36 The de-convolution with the MaxwellBoltzmann distribution gives an O+ average kinetic energy, relative to the center of mass, of ∼ 0.038 eV. This result is achieved by numerical integration, assuming that the O+ distribution in the center of mass can be also approximated by an exponential and using the result of Ref. 35

0.02 eV (G(0.2)), and 1.2 ± 0.3 eV (G(1.2)). The cross sections corresponding to the three distributions, σexpo , σG(0.2) and σG(1.2) , as well as those for the total cross section, σO+ , were obtained as described previously. 29–33

Figure 1: Ratios (squares) between the O+ yield for different time delays t and the O+ yield for the minimum time delay t0 of 300 ns for (a) 30 eV and (b) 450 eV. The fit to the data (black lines) is given by a single exponential distribution for 30 eV, Expo, and by a sum of one exponential, Expo (blue lines), one Gaussian centered at 0.2 eV, G(0.2) (green lines) and one Gaussian centered at 1.2 eV, G(1.2) (red lines) distributions, for 450 eV. These energy distributions are displayed in panels (c) and (d) as a function of the O+ kinetic energy.

Results and Discussion Figure 2 shows our findings. The measured ratios σexpo /σO+ and (σG(0.2) + σG(1.2) )/σO+ are displayed in panels (a) and (b), respectively, as a function of the impact energy. These ratios are compared with the ratios obtained from coincidence measurements for the O+ production by single (a) and double (b) ionization events as reported by Montenegro et al. 24 and King and Price. 28 This comparison shows that the kinetic


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Figure 3: Allowed values (bars) of the kinetic energy release, Q, for a concerted three-body decay compatible with a translational kinetic energy of 0.038 eV for O+ , as a function of the bending angle θ between the two released Hydrogens. The horizontal band represents the values of Q for 28.1 < ∆E < 32.3 eV (see text). These constraints imply that fragmentation occurs for θ > 152o . The uncertainties related to de DETOF adjustment procedure is indicated by error bars.

Figure 2: Ratios of the main structures found in the kinetic energy distribution associated to the O+ recoil ion compared to the yields for the single and double ionization contributions to the O+ fragment as a function of the electron impact energy. (a) σexpo /σO+ (circles - this work), single ionization coincidence measurements by Montenegro et al. 24 (squares) and King and Price 28 (triangles). (b) (σG(0.2) + σG(1.2) )/σO+ (circles - this work), double ionization coincidence measurements by Montenegro et al. 24 (squares) and King and Price 28 (triangles). The lines are to guide the eye.

Q = ∆E − Eb − Ip − Eint − Ee ,

(1)

where ∆E is the energy lost by the impinging electron, Eb = 9.55 eV is the dissociation energy to split H2 O into H0 + O0 + H0 , Ip = 13.62 eV is the Oxygen ionization energy, Eint is the internal energy of the products and Ee is the kinetic energy of the ejected electron. Assuming ∆E ∼ 28.1 eV for the O+ appearance energy, 37 Ee ∼ 0 near the 2a1 vertical ionization threshold and all products in the ground state (Eint = 0), Eq. 1 gives Q ∼ 4.9 eV. Figure 3 shows that this value for Q is only compatible with a strong angular bond rearrangement with the two Hydrogens being ejected with θ > 152o . Fragmentation from higher energy states composing the 2a1 band gives a larger kinetic energy release, reaching Q ∼ 9.1 eV for ∆E = 32.3 eV, the vertical ionization energy. In this case, conservation of energy and momentum together

(with β =1), relating the fragment energy in the CM system with the corresponding distribution in the laboratory, due to the thermal motion of the parent molecule. This very narrow range is a strong constraint for the three-body kinematics. Indeed it limits the angular dependence of the maximum kinetic energy difference between the two ejected Hydrogens and, as a consequence, the range of the available total kinetic energy release, Q(θ). This is shown in Fig. 3. It is clear that only high values of θ allow a large range for Q. That is, the value of Q can define the break-up geometry. The range of possible values for Q can be estimated by energy conservation:


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with our findings restricts θ > 159o , keeping the whole picture essentially unchanged. Although highly unlikely, 37,38 the above three-body decay may include excited states of O+ . In the case of the 2 D first excited state, Eint = 3.24 eV. For ∆E ∼ 28.1 eV, the bond angle rearrangement has weaker kinematic restrictions, with a wider angular range of θ > 128o . Under these same assumptions, the 2 P excited state (Eint = 5.02 eV) is not allowed from energy conservation. Small uncertainties associated to the adjustments inherent in the DETOF method are not able to change this scenario. The orbital 2a1 consists mostly of the 2s orbital of Oxygen. A vacancy in this orbital suddenly decreases the Oxygen nuclear screening to the outermost electrons, causing these electrons to be pulled in the direction of the Oxygen nucleus. The shielding between the two Hydrogen nuclei decreases accordingly and an induction of strong bending vibrational modes is expected. To the authors’ knowledge, what was not previously devised is that the satellite decay also causes such strong bending excitations as shown in our findings. Our results provide a strong support that the three-body fragmentation H0 + O+ + H0 essentially occurs within the linear geometry of the molecular ion, leaving the O+ ion near at rest. Previous indications of fast bond rearrangement in single ionization of water came from observation of the H+ 2 product from electron 24,37,39 or proton 40 impact. For electron impact, our results show that the cross section for the expanding bending fragmentation giving H + O+ + H is more than one order of magnitude larger than that for the contracting bending fragmentation mode giving H+ 2.

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supra-thermal narrow component which has its threshold below the vertical ionization energy of the orbital 2a1 and can be assigned to satellites one-electron-two-vacancies excited states; (ii) this supra-thermal distribution is associated with a large angular bond rearrangement, indicating fragmentation near the linear configuration of the water molecular ion; (iii) this suprathermal distribution has its dynamic behavior absolute value and energy dependence of the associated cross section - identical with that for the single ionization of water and can be assigned as essentially responsible for the H0 + O+ + H0 fragmentation channel, accounting for ∼50% of the total O+ produced; (iv) the more energetic kinetic energy distributions for the O+ fragment can be associated to the Auger and two-steps double ionization processes; (v) as the Auger decay and geometry rearrangement are in the 10−15 s time scale, 41 and, at our highest measured impact energy, the collision time is within the attosecond time scale, the whole rearrangement process is clearly post-collisional and should be the same for ionization by swift heavy ions or photons as well.

Author Information Corresponding Author * [email protected]

Notes The authors declare no competing financial interest. Acknowledgement This work has been partially supported by projects 301782/20121 (Conselho Nacional de Desenvolvimento Cient´ıfico e Tecnológico - CNPq - Brazil) and E-26/102.976/2011 (Funda¸cão de Amparo a Pesquisa do Estado do Rio de Janeiro FAPERJ - Brazil).

Conclusions In conclusion, the DETOF technique was used to explore three-body fragmentation resulting in a single ion and two neutral species. This study takes advantage of the sensitivity of this technique to obtain translational kinetic energy of supra-thermal ions usually not accessible by other techniques. We found that (i) the kinetic energy distribution of O+ ions has a

References (1) Abolfath R.M.; Carlson D.J.; Chen Z.J.; Nath R. A molecular dynamics simulation


6

Page 7 of 9

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(10) Reeves K.G.; Kanai Y. Electronic excitation dynamics in liquid water under proton irradiation. Scientific Reports 2017, 7 40379.

of DNA damage induction by ionizing radiation. Phys. Med. Biol. 2013, 58, 71437157. (2) Yoshimura M.; Itasaka S.; Harada H.; Hiraoka M. Microenvironment and radiation therapy. BioMed Research International 2013, 2013, 685308.

(11) Sansone G.; Pfeifer T.; Simeonidis K.; Kuleff A.I. Electron correlation in real time. Phys. Chem. Chem. Phys. 2012, 13, 661-680.

(3) Shematovich V.I. Ionization chemistry in H2 O-dominated atmospheres of icy moons. Solar System Res. 2008, 42, 473487.

(12) Kuleff A.I.; Kryzhevoi N.V.; Pernpointer M.; Cederbaum L.S. Core ionization initiates subfemtosecond charge migration in the valence shell of molecules. Phys. Rev. Lett. 2016, 117, 093002.

(4) Blanc M.; Andrews D.J.; Coates A.J.; Hamilton D.C.; Jackman C.M.; Jia X.; Kotova A.; Morooka M.; Smith H.T.; Westlake J.H. Saturn plasma sources and associated transport processes. Space. Sci. Rev. 2015, 192, 237-283.

(13) Gagnon E.; Ranitovic P.; Tong X.-M.; Cocke C.L.; Murnane M.M.; Kapteyn H.C.; Sandhu A.R. Soft X-ray driven femtosecond molecular dynamics. Science 2007, 317, 1374-1378.

(5) Haddad G.N.; Samson J.A.R. Total absorption and photoionization cross sections of water vapor between 100 and 1000 ˚ A. J. Chem. Phys. 1986, 84, 6623-6626.

(14) Suárez J.; Méndez L.; Rabadán I. Nonadiabatic quantum dynamics predissocia˜ 2 B2 ). J. Phys. Chem. Lett. tion of H2 O+ (B 2015,6, 72-76.

(6) Itikawa Y.; Mason N.J. Cross sections for electron collisions with water molecules. Phys. Chem. Ref. Data 2005, 34, 1-22.

(15) Cederbaum L.S.; Domke W.; Schirmer J.; von Niessen W. Many-body effects in valence and core photoionization of molecules. Physica Scripta 1980, 21, 481491.

(7) Werner U.; Beckord K.; Becker J.; Lutz H.O. 3D Imaging of the collisioninduced coulomb fragmentation of water molecules. Phys. Rev. Lett. 1995, 74, 1962-1965.

(16) Truong S.Y.; Yencha A.J.; Juarez A.M.; Cavanagh S.J.; Bolognesi P.; King G.C. Threshold photoelectron spectroscopy of H2 O and D2 O over the photon energy range 12-40 eV. Chem. Phys. 2009, 355, 183-193.

(8) Luna H.; de Barros A.L.F.; Wyer J.A.; Scully S.W.J.; Lecointre J.; Garcia P.M.Y.; Sigaud G.M.; Santos A.C.F.; Senthil V.; Shah M.B.; et al. Watermolecule dissociation by proton and hydrogen impact. Phys. Rev. A 2007, 75, 042711.

(17) Zhou X.; Ranitovic P.; Hogle C.W.; Eland J.H.D.; Kapteyn H.C.; Murnane M.M. Probing and controlling non-BornOppenheimer dynamics in highly excited molecular ions. Nature Physics 2012, 8, 232-237.

(9) Gervais B.; Beuve M.; Olivera G.H.; Galassi M.E. Numerical simulation of multiple ionization and high LET effects in liquid water radiolysis. Rad. Phys. Chem. 2006, 75, 493-513.

(18) Lépine F.; Ivanov M.Y.; Vrakking M.J.J. Attosecond molecular dynamics: fact or fiction? Nature Photonics 2014, 8, 195204.


7


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 9

(28) King S.J.; Price S.D. Electron ionization of H2 O. Int. J. Mass Spectrom. 2008, 277, 84-90.

(19) Ning C.G.; Hajgato B.; Huang Y.R.; Zhang S.F.; Liu K.; Luo Z.H.; Knippenberg S.; Deng J.K.; Deleuze M.S. High resolution electron momentum spectroscopy of the valence orbitals of water. Chem. Phys. 2008, 343, 19-30.

(29) Ferreira Natalia; Sigaud L.; de Jesus V.L.B.; Rocha A.B.; Coutinho L.H.; Montenegro E.C. Fragmentation of 14,15 N2 by electron impact investigated using a timedelayed spectroscopic technique. Phys. Rev. A 2012, 86, 012702.

(20) Banna M.S.; McQuaide B.H.; Malutzki R.; Schmidt V. The photoelectron spectrum of water in the 30-140 eV photon energy range. J. Chem. Phys. 1986, 84, 4739-4744.

(30) Ferreira Natalia; Sigaud L.; Montenegro E.C. Molecular fragmentation by electron impact investigated using a time delayed spectroscopic technique. J. Phys.: Conf. Ser. 2014, 488, 012042.

(21) Jones D.B.; Yamazaki M.; Watanabe N.; Takahashi M. Electron-impact ionization of the water molecule at large momentum transfer above the doubleionization threshold. Phys. Rev. A 2011, 83, 012704.

(31) Sigaud L.; de Jesus V.L.B.; Ferreira Natalia; Montenegro E.C. A novel doublefocusing time-of-flight mass spectrometer for absolute recoil ion cross sections measurements. Rev. Sci. Instrum. 2016, 87, 083112.

(22) Scully S.W.J.; Wyer J.A.; Senthil V.; Shah M.B.; Montenegro E.C. Autodissociation of doubly charged water molecules. Phys. Rev. A 2006, 73, 040701(R).

(32) Sigaud L.; Ferreira Natalia; Montenegro E.C. Absolute cross sections for O2 dication production by electron impact. J. Chem. Phys. 2013, 139, 024302.

(23) Dal Cappello C; Mkhanter R.E.; Hervieux P.A. Mechanisms of double ionization of atoms by electron impact. Phys. Rev. A 1998, 57, R693.

(33) Sigaud L.; Montenegro E.C. Cross sections for the CH+ 2 formation pathways via CH4 fragmentation by electron impact. J. Phys. B: At. Mol. Opt. Phys. 2015, 48, 115207.

(24) Montenegro E.C.; Scully S.W.J.; Wyer J.A.; Senthil V.; Shah M.B. Evaporation, fission and auto-dissociation of doubly charged water. J. Electron Spectrosc. Relat. Phenom. 2007, 155, 81-85.

(34) Cameron A.C.; Windmeijer F.A.G. An R-squared measure of goodness of fit for some common nonlinear regression models. J. of Econometrics; 1997, 77, 329-342.

(25) Montenegro E.C. Fragmentation of water by heavy ions. J. Phys.: Conf. Ser. 2009, 194, 012049.

(35) Chantry P.J.; Schulzt G.J. Kinetic-energy distribution of negative ions formed by dissociative attachment and the measurement of the electron affinity of oxygen. Phys. Rev. 1967, 156, 134-141.

(26) Tavares A.C.; Luna H.; Wolff W.; Montenegro E.C. Double ionization of water molecules induced by swift protons. Phys. Rev. A 2015, 92, 032714. (27) Tan K.H.; Brion C.E.; Van Der Leeuw Ph.E.; Van Der Wiel M.J. Absolute oscillator strengths (10-60 eV) for the photoabsorption, photoionisation and fragmentation of H2 O. Chem. Phys. 1978, 79, 299309.

(36) Maul C.; Gericke K.-H. Aspects of photoinduced molecular three-body decay. J. Phys. Chem. A 2000, 104, 2531-2541. (37) Mann M.M.; Hustrulid A.; Tate J.T. The ionization and dissociation of water vapor


8

Page 9 of 9

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and ammonia by electron impact. Phys. Rev. 1940, 58, 340-347. (38) Richardson P.J.; Eland J.H.D.; Fournier P.G.; Cooper D.L. Spectrum and decay of the doubly charged water ion. J. Chem. Phys. 1986, 84, 3189-3194. (39) Straub H.C.; Lindsay B.G.; Smith K.A.; Stebbings R.F. Absolute partial cross sections for electron-impact ionization of H2 O and D2 O from threshold to 1000 eV. J. Chem. Phys. 1998, 108, 109-116.

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(40) Ben-Itzhak I.; Sayler A.M.; Leonard M.; Maseberg J.W.; Hathiramani D.; Wells E.; Smith M.A.; Xia J.; Want P.; Carnes K.D.; et al. Bond rearrangement caused by sudden single and multiple ionization of water molecules. Nucl. Instrum. Methods B 2005, 233, 284-292. (41) Singh R.; Bhatt P.; Yadav N.; Shanker R. Kinematics and dissociation dynamics of a water molecule under the impact of 10 keV electrons. J. Phys. B: At. Mol. Opt. Phys. 2013, 46, 085203.


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Three-Body Fragmentation from Single Ionization of Water by Electron

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