Cluster sputtering: complete fragmentation of large ammonia clusters by photons and electrons

Schütte, S.; Buck, U.

doi:10.1007/s003399900390

Cited by 3 publications

(4 citation statements)

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“…Apparently the previous measurement was hampered by fragmentation caused by multiphoton processes. 15 The results for the larger clusters proved to be correct. We have added the new results for the higher collision energy also in Table I.…”

Section: Methodsmentioning

confidence: 86%

Intermolecular vibrations of large ammonia clusters from helium atom scattering

Beu¹,

Steinbach²,

Buck³

2002

The Journal of Chemical Physics

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The excitation of the low-energy intermolecular modes of ammonia clusters by helium atom scattering has been calculated using classical trajectories. The energy transfer is investigated as a function of scattering angle ͑from 10°to 90°͒, collision energy ͑94.8 and 50.5 meV͒, cluster size (nϭ18, 100, 1000͒, and cluster temperature (T c ϭ1 K, 30-50 K, and 105 K͒. It is observed that predominantly the mode at 7 meV and to a lesser extent also the one at 12 meV are excited. These are surface modes that mainly originate from the angular motion of three adjacent N atoms. The excitation is nearly independent of the cluster size and the probability for multiphonon excitation steadily increases with increasing deflection angle. This trend is even strengthened by increasing the collision energy. The role of the cluster temperature is to broaden the energy transfer distribution with increasing values. The calculations are compared with previous and new measurements presented here of the double-differential cross sections (d/d) ⌬E of ammonia clusters of average size ͗n͘ϭ92 at two collision energies and ͗n͘ϭ1040 at one energy. While the general trends in the angular and energy dependence could be well reproduced, the correct cluster temperature was crucial in getting good agreement at the lower collision energy for nϭ100. At the higher collision energy, the large energy transfer is not reproduced, probably a shortcoming of the potential models to account correctly for the anharmonicity of the strong multiquantum excitations.

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Section: Methodsmentioning

confidence: 86%

Intermolecular vibrations of large ammonia clusters from helium atom scattering

Beu¹,

Steinbach²,

Buck³

2002

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…This could indicate that successive absorption of multiple photons causes the E IR -dependent decrease. [110] In contrast to this, the IR-induced signal gain for excitation at 3200 cm −1 remains nearly unchanged with increasing E IR and is only slightly reduced with increasing ∆t. This is consistent with the temporal evolution of the 3200 cm −1 data shown in the previous section and could indicate a coexistence of crystalline and amorphous clusters.…”

Section: Pulse Energy Dependencementioning

confidence: 86%

“…[108] Since then, TOF mass analyzers have become widely used and appreciated for their unlimited m z size range, [102,109] which makes TOF-MS suitable for the study of weakly-bound clusters with hundreds to thousands of constituent molecules. [34,110] The mass separation in a TOF mass spectrometer is achieved by acceleration of equally charged species with different masses m to different terminal velocities v by conversion of the potential energy E el of a charge q = z • e within an electric field with the electric potential difference U a 0 to kinetic energy E kin . [102] E kin = E el (2.9)…”

Section: Time-of-flight Mass Spectrometrymentioning

confidence: 99%