Fragmentation dynamics of CO(2)(3+) investigated by multiple electron capture in collisions with slow highly charged ions.
TL;DR: The total energy deposited in the molecular ion is a control parameter which switches between three distinct fragmentation pathways: the sequential fragmentation in which the emission of an O(+) ion leaves a rotating CO(2+) ion behind that fragments after a time delay, the Coulomb explosion and an in-between fragmentation--the asynchronous dissociation.
Abstract: Fragmentation of highly charged molecular ions or clusters consisting of more than two atoms can proceed in a one step synchronous manner where all bonds break simultaneously or sequentially by emitting one ion after the other. We separated these decay channels for the fragmentation of CO(2)(3+) ions by measuring the momenta of the ionic fragments. We show that the total energy deposited in the molecular ion is a control parameter which switches between three distinct fragmentation pathways: the sequential fragmentation in which the emission of an O(+) ion leaves a rotating CO(2+) ion behind that fragments after a time delay, the Coulomb explosion and an in-between fragmentation--the asynchronous dissociation. These mechanisms are directly distinguishable in Dalitz plots and Newton diagrams of the fragment momenta. The CO(2)(3+) ions are produced by multiple electron capture in collisions with 3.2 keV/u Ar(8+) ions.
Citations
More filters
TL;DR: It is demonstrated that it is possible to experimentally select distinct molecular-fragmentation pathways in which the core hole can be considered as either localized on one sulfur atom or delocalized between two indistinguishable sulfur atoms.
Abstract: Electronic core levels in molecules are highly localized around one atomic site. However, in single-photon ionization of symmetric molecules, the question of core-hole localization versus delocalization over two equivalent atoms has long been debated as the answer lies at the heart of quantum mechanics. Here, using a joint experimental and theoretical study of core-ionized carbon disulfide (CS2), we demonstrate that it is possible to experimentally select distinct molecular-fragmentation pathways in which the core hole can be considered as either localized on one sulfur atom or delocalized between two indistinguishable sulfur atoms. This feat is accomplished by measuring photoelectron angular distributions within the frame of the molecule, directly probing entanglement or disentanglement of quantum pathways as a function of how the molecule dissociates.
58 citations
TL;DR: A novel method is demonstrated that enables the clear separation of sequential and concerted breakup and finds that the first step of sequential breakup is tightly aligned along the laser polarization and identify the likely electronic states of the intermediate dication that undergo unimolecular dissociation in the second step.
Abstract: A key question concerning the three-body fragmentation of polyatomic molecules is the distinction of sequential and concerted mechanisms, i.e., the stepwise or simultaneous cleavage of bonds. Using laser-driven fragmentation of OCS into ${\mathrm{O}}^{+}+{\mathrm{C}}^{+}+{\mathrm{S}}^{+}$ and employing coincidence momentum imaging, we demonstrate a novel method that enables the clear separation of sequential and concerted breakup. The separation is accomplished by analyzing the three-body fragmentation in the native frame associated with each step and taking advantage of the rotation of the intermediate molecular fragment, ${\mathrm{CO}}^{2+}$ or ${\mathrm{CS}}^{2+}$, before its unimolecular dissociation. This native-frame method works for any projectile (electrons, ions, or photons), provides details on each step of the sequential breakup, and enables the retrieval of the relevant spectra for sequential and concerted breakup separately. Specifically, this allows the determination of the branching ratio of all these processes in ${\mathrm{OCS}}^{3+}$ breakup. Moreover, we find that the first step of sequential breakup is tightly aligned along the laser polarization and identify the likely electronic states of the intermediate dication that undergo unimolecular dissociation in the second step. Finally, the separated concerted breakup spectra show clearly that the central carbon atom is preferentially ejected perpendicular to the laser field.
51 citations
TL;DR: The ground state nuclear wave function of the dimer, trimer, and tetramer is determined by measuring all momentum vectors of the singly charged ions in coincidence and the bond angles are retrieved by applying a classical numerical simulation.
Abstract: We Coulomb explode argon and neon dimers, trimers, and tetramers by multiple ionization in an ultrashort 800 nm laser pulse. By measuring all momentum vectors of the singly charged ions in coincidence, we determine the ground state nuclear wave function of the dimer, trimer, and tetramer. Furthermore we retrieve the bond angles of the trimer in position space by applying a classical numerical simulation. For the argon and neon trimer, we find a structure close to the equilateral triangle. The width of the distribution around the equilateral triangle is considerably wider for neon than for argon.
46 citations
TL;DR: An experimental route to identify and separate geometric isomers by means of coincident Coulomb explosion imaging is presented, allowing isomer-resolved photoionization studies on isomerically mixed samples.
Abstract: An experimental route to identify and separate geometric isomers by means of coincident Coulomb explosion imaging is presented, allowing isomer-resolved photoionization studies on isomerically mixed samples. We demonstrate the technique on cis/trans 1,2-dibromoethene (C2H2Br2). The momentum correlation between the bromine ions in a three-body fragmentation process induced by bromine 3d inner-shell photoionization is used to identify the cis and trans structures of the isomers. The experimentally determined momentum correlations and the isomer-resolved fragment-ion kinetic energies are matched closely by a classical Coulomb explosion model.
36 citations
TL;DR: For the T-shaped N(2)Ar dimer, both sequential and direct triple-ionization-induced three-body breakups are observed and other structures are found to coexist with the dominating T- shaped one for O( 2)Ar and O (2)Xe.
Abstract: We use intense femtosecond laser pulses to multiply ionize and directly image the structures of N(2)Ar, O(2)Ar, and O(2)Xe dimers by coincidently measuring the momenta of the fragment ions. All these dimers are found to have an equilibrium T-shaped structure in which the bond of the diatomic molecule is perpendicular to the dimer axis. The equilibrium distance between the rare-gas atom and the center-of-mass of the diatomic molecule is estimated to be R(N2-Ar) ~ 3.86 A, R(O2-Ar) ~ 3.65 A, and R(O2-Xe) ~ 4.07 A, respectively. For the T-shaped N(2)Ar dimer, both sequential and direct triple-ionization-induced three-body breakups are observed. In contrast to N(2)Ar dimer, other structures are found to coexist with the dominating T-shaped one for O(2)Ar and O(2)Xe.
34 citations
References
More filters
TL;DR: In this article, the authors present a comprehensive set of FDCSs for single ionization of atoms by ion-impact, the most basic atomic fragmentation reaction, brought new insight, a couple of surprises and unexpected challenges to theory at keV to GeV collision energies.
Abstract: Recoil-ion and electron momentum spectroscopy is a rapidly developing technique that allows one to measure the vector momenta of several ions and electrons resulting from atomic or molecular fragmentation. In a unique combination, large solid angles close to 4π and superior momentum resolutions around a few per cent of an atomic unit (a.u.) are typically reached in state-of-the art machines, so-called reaction-microscopes. Evolving from recoil-ion and cold target recoil-ion momentum spectroscopy (COLTRIMS), reaction-microscopes—the `bubble chambers of atomic physics'—mark the decisive step forward to investigate many-particle quantum-dynamics occurring when atomic and molecular systems or even surfaces and solids are exposed to time-dependent external electromagnetic fields. This paper concentrates on just these latest technical developments and on at least four new classes of fragmentation experiments that have emerged within about the last five years. First, multi-dimensional images in momentum space brought unprecedented information on the dynamics of single-photon induced fragmentation of fixed-in-space molecules and on their structure. Second, a break-through in the investigation of high-intensity short-pulse laser induced fragmentation of atoms and molecules has been achieved by using reaction-microscopes. Third, for electron and ion-impact, the investigation of two-electron reactions has matured to a state such that the first fully differential cross sections (FDCSs) are reported. Fourth, comprehensive sets of FDCSs for single ionization of atoms by ion-impact, the most basic atomic fragmentation reaction, brought new insight, a couple of surprises and unexpected challenges to theory at keV to GeV collision energies. In addition, a brief summary on the kinematics is provided at the beginning. Finally, the rich future potential of the method is briefly envisaged.
1,375 citations
TL;DR: The cold target recoil ion momentum spectroscopy (COLTRIMS) is a momentum space imaging technique for the investigation of the dynamics of ionizing ion, electron or photon impact reactions with atoms or molecules as mentioned in this paper.
985 citations
TL;DR: In this paper, the relation between the spin and parity of the τ-meson and the distribution of decay configurations is obtained for some simple cases, where the unlike outgoing meson is not distinguished.
Abstract: A convenient method of representation is proposed (§ 2) for data on τ-meson decay configurations, applicable when the unlike outgoing π-meson is not distinguished. The relation between the spin and parity of the τ-meson and the distribution of decay configurations is obtained for some simple cases. The hypothesis that the τ- and X-mesons are identical requires a non-zero spin for this particle and the available data on τ-meson decay does not exclude this possibility. However, observations in which the unlike outgoing π-meson is not distinguished are relatively ineffective in discriminating between the various possibilities. The distortions which strong meson-meson attraction may produce in τ-decay configurations are discussed ; the present data offers no evidence on this effect.
528 citations
21 Jan 2002-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the authors designed and tested a complete imaging system consisting of an MCP position readout with helical wire delaylines, single-unit amplifier box and PC-controlled time-to-digital converter (TDC) readout.
Abstract: New applications for single particle and photon detection in many fields require both large area imaging performance and precise time information on each detected particle. Moreover, a very high data acquisition rate is desirable for most applications and eventually the detection and imaging of more than one particle arriving within a microsecond is required. Commercial CCD systems lack the timing information whereas other electronic microchannel plate (MCP) read-out schemes usually suffer from a low acquisition rate and complicated and sometimes costly read-out electronics. We have designed and tested a complete imaging system consisting of an MCP position readout with helical wire delaylines, single-unit amplifier box and PC-controlled time-to-digital converter (TDC) readout. The system is very flexible and can detect and analyse position and timing information at single particle rates beyond 1 MHz. Alternatively, multihit events can be collected and analysed at about 20 kHz rate. We discuss the advantages and applications of this technique and then focus on the detector’s ability to detect and analyse multiple hits. r 2002 Elsevier Science B.V. All rights reserved.
192 citations
TL;DR: In this paper, the deformation of the geometrical structure of the potential energy surfaces induced by the Coulomb explosion process was investigated by momentum imaging of the fragment of a light-dressed potential energy surface.
Abstract: Ultrafast deformation of geometrical structure of ${\mathrm{CO}}_{2}$ in an intense laser field ( $11\mathrm{PW}/{\mathrm{cm}}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}11\ifmmode\times\else\texttimes\fi{}{10}^{15}\mathrm{W}/{\mathrm{cm}}^{2}$) was investigated by momentum imaging of the fragment ${\mathrm{O}}^{p+}$ and ${\mathrm{C}}^{q+}$ $(p,q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1\char21{}3)$ ions produced from ${\mathrm{CO}}_{2}^{z+}$ through the Coulomb explosion processes, ${\mathrm{CO}}_{2}^{z+}\ensuremath{\rightarrow}{\mathrm{O}}^{p+}+{\mathrm{C}}^{q+}+{\mathrm{O}}^{r+}$ $(z\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}p+q+r)$ The observed large mean amplitude along the $\ensuremath{\angle}\mathrm{O}\char22{}\mathrm{C}\char22{}\mathrm{O}$ bond angle ( $\ensuremath{\sim}40\ifmmode^\circ\else\textdegree\fi{}$) was attributed to the ultrafast bending motion induced on the light-dressed potential energy surfaces
121 citations