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444 results on '"Echt O"'

151. General discussion

Author

Jarrold, M. F., primary, Kaldor, A., additional, Berry, R. S., additional, Castleman, A. W., additional, Lifshitz, C., additional, Kroto, H. W., additional, Whetten, R. L., additional, Langridge-Smith, P. R. R., additional, Simons, J. P., additional, Meiwes-Broer, K-H., additional, Naaman, R., additional, Murrell, J. N., additional, Haberland, H., additional, Miller, J. C., additional, Benfield, R. E., additional, Martin, T. P., additional, Echt, O., additional, Michl, J., additional, Märk, T. D., additional, and Alonso, J. A., additional

Published
1990
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152. Collisional formation and dissociation of <f>Na@C60+</f>

Author

Deng, R. and Echt, O.

Subjects
*SODIUM ions, *DISSOCIATION (Chemistry), *COLLISIONS (Nuclear physics)
Abstract

The dissociation rate constant of a microcanonical ensemble of endohedral Na@C60+, formed by gas-phase collisions, is determined to be 94 000 s−1 when the internal excitation energy reaches 49.1±0.5 eV. A model that includes radiative cooling and a distribution of energies, accurately reproduces the yield of Na@C60+ from its appearance at 29.6 eV to its disappearance above 55 eV. Assuming an Arrhenius factor of ν0=5×1019 s−1 we derive a dissociation energy of 10.17±0.02 eV (statistical error). The abruptness of the breakdown graph implies a lower limit for ν0. [Copyright &y& Elsevier]

Published
2002
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153. Evaporation rates for Na clusters.

Author

Borggreen, J., Chandezon, F., Echt, O., Grimley, H., Hansen, K., Hansen, P.M., and Ristori, C.

Abstract

Na clusters in the size range of 50–400 atoms are led to evaporate in a heat bath with controlled temperature. For specific cluster sizes just above closed shells, decay rates are measured as a function of temperature. They agree with an Arrhenius law and allow absolute separation energies to be extracted. [ABSTRACT FROM AUTHOR]

Published
2000
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155. Resonance-enhanced multiphoton ionization (2+1) of the $$\tilde B$$ and $$\tilde C'$$ states of ammonia.

Author

Stanley, R., Echt, O., and Castleman, A.

Abstract

Resonance-enhanced multiphoton ionization (REMPI) of the $$\tilde B$$ and $$\tilde C'$$ states of NH in a pulsed supersonic molecular beam was observed at 304-340 nm, using the multiphoton-ionization mass-spectrometer system described herein. The observed features are the result of a 2+1 MPI process and correspond quite well with the reported 3+1 MPI of NH in the literature from the ground state of opposite parity. [ABSTRACT FROM AUTHOR]

Published
1983
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157. Trapping of low energy electrons at preexisting, cold water clusters.

Author

Knapp, M., Echt, O., Kreisle, D., and Recknagel, E.

Subjects
*ELECTRONS, *CLUSTER theory (Nuclear physics), *MOLECULAR beams
Abstract

Long-lived water cluster anions [(H2O)-n, n≥11, and (D2O)-n, n≥12] can be formed by electron attachment to a beam of preformed, neutral clusters; collisional stabilization is not required. Attachment occurs resonantly at or very close to 0 eV incident electron energy; the ion yield is unexpectedly large. [ABSTRACT FROM AUTHOR]

Published
1986
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160. Efficiency of Thermionic Emission from C<INF>60</INF>

Author

Deng, R. and Echt, O.

Abstract

We have determined the number of delayed electrons emitted from an ensemble of gas-phase C60, excited at 355 nm with light from an unfocused pulsed Nd:YAG laser. Delayed electrons are detected by single particle counting and integrated over a time interval of 0.1 μs ≤ t ≤ 80 μs. At low laser fluence I, the electron number scales as Ip with p = 6.0 ± 0.4. It approaches saturation at a maximum laser fluence of 100 mJ/cm2, equivalent to a power density of 14 MW/cm2, where delayed electron emission reaches a probability of 2.6 ± 1.1% per multiphoton-excited C60. This experimental value is interpreted as a lower limit to the quantum efficiency for electron emission from C60; it provides an upper limit to the efficiency of competing reactions such as dissociation of C60 into C58 + C2. The dependence of the electron number on the temperature of the fullerene source is in good agreement with the number density of C60 in the molecular beam, as computed from published equilibrium vapor pressures.

Published
1998

161. Resonance-enhanced multiphoton ionization (2+1) of the <img src="/fulltext-image.asp?format=htmlnonpaginated&src=H401K70G2PJ55036_html\340_2004_Article_BF00688773_TeX2GIFIE1.gif" border="0" alt=" $$\tilde B$$ " /> and <img src="/fulltext-image.asp?fo

Author

Stanley, R. J., Echt, O., and Castleman, A. W.

Abstract

Resonance-enhanced multiphoton ionization (REMPI) of the " and " states of NH3 in a pulsed supersonic molecular beam was observed at 304–340 nm, using the multiphoton-ionization mass-spectrometer system described herein. The observed features are the result of a 2+1 MPI process and correspond quite well with the reported 3+1 MPI of NH3 in the literature from the ground state of opposite parity.

Published
1983
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162. Mass spectrometric size analysis of N2O-clusters

Author

Echt, O., Knapp, M., Sattler, K., and Recknagel, E.

Abstract

Mass spectra of N2O-clusters in the size rangen?7,000 molecules per cluster, formed in a supersonic beam, have been recorded in a time-of-flight mass spectrometer. The spectra trace the transition from growth by successive monomer addition to growth by cluster coagulation. The influence of the ionization process and the detection probability is discussed.

Published
1983
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163. Impurity-defect configurations in ion-irradiated copper studied by the DPAC-technique with111In

Author

Echt, O., Recknagel, E., Weidinger, A., and Wichert, Th.

Abstract

The structure and dynamics of lattice defects in copper are investigated. The defects have been produced by irradiation with heavy ions of 350 keV between 85 K and 300 K. Three different defect configurations are distinguished by the time differential perturbed angular correlation technique (DPAC) with111In as radioactive probe. Their electric quadrupole coupling constants?Q=e2Qqzz/h are?Q1=116(2)MHz,?Q2=181(3)MHz and?Q3=52(1)MHz. The defects characterized by?Q1 and?Q2 are observed in the temperature range of recovery stage III. The appearance of?Q3 is closely correlated with recovery stage V. The symmetry axis of the electric field gradient associated with this defect-111In configuration points along a crystallographic <111> direction. We attribute this defect to a planar faulted loop, presumably of vacancy type. The influence of irradiating particles and dose on the defect configurations is analyzed.

Published
1978
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164. Formation of long-lived CO−2, N2O−, and their dimer anions, by electron attachment to van der waals clusters

Author

Knapp, M., Echt, O., Kreisle, D., Märk, T.D., and Recknagel, E.

Abstract

CO2−and N2O−anions, which cannot be formed by electron attachment to the corresponding molecules in the gas phase, are formed by dissociative attachment to clusters of CO2and N2O, respectively. The relative yields of the monomer and dimer anions are presented and discussed.

Published
1986
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165. On the role of the II(1/2g) state in spontaneous dissociation of krypton and xenon dimer ions

Author

Fedor, Juraj, Echt, O., Głuch, K., Matt-Leubner, S., Scheier, P., Märk, T.D., Fedor, Juraj, Echt, O., Głuch, K., Matt-Leubner, S., Scheier, P., and Märk, T.D.

Abstract

We have measured kinetic-energy-release distributions (KERD) for spontaneous dissociation of electronically excited dimer ions of krypton and xenon, formed by electron impact ionization of neutral precursors. The data cannot be reconciled by decay of the strongly bound II(1/2u) state that successfully explains dissociation of and Ne₂⁺ and Ar₂⁺. Instead, the KERD is dominated by contributions from the weakly bound II(1/2g) state that has so far escaped a convincing experimental characterization. The present data can be utilized to assess the accuracy of ab initio potential energy curves of this state.

169. μSR in ferromagnetic and antiferromagnetic dysprosium

Author

Hofmann, W., primary, Kündig, W., additional, Meier, P.F., additional, Patterson, B.D., additional, Rüegg, K., additional, Echt, O., additional, Graf, H., additional, Recknagel, E., additional, Weidinger, A., additional, and Wichert, T., additional

Published
1978
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200. High-resolution kinetic energy release distributions and dissociation energies for fullerene ions Cn+, 42<=n<=90.

Author

Głuch, K., Matt-Leubner, S., Echt, O., Concina, B., Scheier, P., and Märk, T. D.

Subjects
*SCISSION (Chemistry), *SPECTROMETERS, *SPECTRUM analysis instruments, *FULLERENES, *NANOTUBES, *CARBON
Abstract

We have measured the kinetic energy released in the unimolecular dissociation of fullerene ions, Cn+→Cn-2++C2, for sizes 42≤n≤90. A three-sector-field mass spectrometer equipped with two electric sectors has been used in order to ensure that contributions from isotopomers of different masses do not distort the experimental kinetic energy release distributions. We apply the concept of microcanonical temperature to derive from these data the dissociation energies of fullerene cations. They are converted to dissociation energies of neutral fullerenes with help of published adiabatic ionization energies. The results are compared with literature values. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2004
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