D. Kella

Electron photodetachment cross sections of small carbon clusters: evidence for nonlinear isomers.

Absolute cross sections for photodetachment of negative carbon clusters are reported for Cn (n = 3, ..., 8). The results indicate that various neutral isomers exist, some with electron affinities as low as 1 electron volt. The method of production plays an important role in the characteristics of carbon clusters.

A system for Coulomb explosion imaging of small molecules at the Weizmann Institute

Abstract A description of a system for molecular structure imaging at the Weizmann Institute is presented. A novel method of controlled laser beam photo detachment inside the high voltage terminal of a tandem accelerator, enabling the study of neutral fast molecules by the Coulomb Explosion Imaging technique, is described. Also, a new type of three dimension multiparticle detector is presented.

The structure of small carbon clusters

New non linear isomers of C n forn=4, 5, 6 have been observed using the combination of the laser photodetachment technique and the Coulomb Explosion Imaging method. Electron affinities of these isomers were found to be lower than the corresponding known linear isomers. The structure of low electron affinity C4 isomer was found to be rhombic in accordance with recent theory. Indications for the non linearity of the low electron affinity isomers of C5 and C6 are also presented.New non linear isomers of Cn forn=4, 5, 6 have been observed using the combination of the laser photodetachment technique and the Coulomb Explosion Imaging method. Electron affinities of these isomers were found to be lower than the corresponding known linear isomers. The structure of low electron affinity C4 isomer was found to be rhombic in accordance with recent theory. Indications for the non linearity of the low electron affinity isomers of C5 and C6 are also presented.

The structure of carbon clusters as studied by the coulomb explosion method

The Coulomb explosion imaging (CEI) method has been used to determine the structure and photochemistry of carbon clusters. The cyclic isomer of Cn for 4 ⩽n⩽ 6 was observed, using a combination of laser photo-detachment techniques and the CEI method. The cyclic C4 electron affinity was found to be 2.1 ± 0.1 eV, more than one eV lower than the electron affinity of the linear isomer. Upper limits for the electron affinities of the cyclic C5, and C6 were also established.

A detailed study of conformations in the ground state of CH+4

The results of Coulomb explosion imaging for cold CH+4 molecular ions are converted to the molecular conformation probability density. This is the first complete conversion of such data for a relatively complex molecule. The results are compared with the corresponding predicted potential energy surfaces which manifest a Jahn–Teller symmetry breaking. The density of conformations along a nuclear rearrangement path is deduced and the comparison with the theory is satisfactory in almost every respect, except for the density near the minimum of the theoretical potential

Observation of laser excitation of rhombic C4 using the coulomb explosion method

The combination of laser photodetachment of C4− and the Coulomb Explosion Imaging method was applied for the investigation of the structure of several C4 isomers and was correlated with their measured electron affinities.

Molecular imaging with fast beams

Abstract Three dimensional imaging of the molecular dissociation process in fast collisions is presented with two different setups. One setup is for a fast molecular beam from an accelerator colliding with a gas target. The second setup is for a molecular target system and the collision process is with highly ionized fast beam. The advantages of each system are discussed. The three dimensional imaging of the molecular fragments is done with special detectors that combine the CCD image with time of flight data. An example of the molecular beam measurement is given for an 11 MeV B2 beam.

Carbon cluster imaging at the Weizmann Institute Coulomb explosion system

Abstract The structure of small carbon clusters (Cn, n = 3–8) has been studied using the Coulomb explosion imaging technique. The experimental system is based on the 14 MV Pelletron accelerator at the Weizmann Institute. Negative molecules are accelerated and photodetached by a laser beam inside the high voltage terminal of the accelerator. The neutral molecules are then electron stripped by passing through a thin Formvar target and the resulting atomic ions are collected by a new 3D multiparticle imaging detector. Nonlinear structures of C4 and C5 clusters were observed. New measurements of laser photodetachment thresholds for Cn (n = 3–8) indicate that new compact isomers exist.

The isomers of small carbon clusters

Absolute cross-sections for photodetachment of negative carbon clusters are reported for Cn− (n=3,...,8). These measurements are made using different types of ion sources, which create different isomers. These new results indicate that various negative and neutral isomers exist, some with electron affinities as low as ∼1 eV.