Velocity Map Imaging Spectrometer for Studying the Atomic Cluster Thermodynamics

ZHANG Xujie; SHI Fudong; QIAN Dongbin; ZHANG Dacheng; ZHU Xiaolong; YANG Jie; LI Xinzhong; MA Xinwen

doi:10.11804/NuclPhysRev.33.04.506

Excitation temperature of fragmenting atomic clusters can been extracted from the initial kinetic energies of ionic products. To improve the accuracy of the temperature measurements, we have designed an ionic velocity map imaging spectrometer with high kinetic energy resolution. Firstly, based on the simulations using Simion8.0 software, the high resolution is obtained by adjusting the structure of the electrostatic lenses and collimation of molecular beam. According to theoretical analysis, it is proved that the spectrometer has a well defined kinetic energy resolution. Then, we have studied the delay ionization processes of C₆₀ induced by nanosecond laser. A series of narrowed two-dimensional time-sliced velocity images of the C₆₀⁺ with increasing the delayed time were recorded. Analysis revealed that Coulomb force between C₆₀⁺ clusters in same laser shots will broadening the transverse distribution of 2D image. Considering the influence of Coulomb force on initial kinetic energy of C₆₀⁺ clusters, the high resolution has been proved by analysing the negative relationship between Coulomb force and delayed time. It indicates that the establishment of the spectrometer builds up a good basis for next experiments on the studies for molecular thermodynamics in atomic clusters.

Velocity Map Imaging Spectrometer for Studying the Atomic Cluster Thermodynamics

1. School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023, Henan, China;

2. Institute of Modern Physics, Chinese Academy Sciences, Lanzhou 730000, China;

3. College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China

Funds: The National Natural Science Foundation of China (U1232122,10904152)

Received Date: 2015-12-18

Rev Recd Date: 2016-01-20

Publish Date: 2016-12-20

Key words:

atomic cluster /
excitation temperature /
ionic velocity map imaging spectrometer /
kinetic energy resolution /
delay ionization

Abstract: Excitation temperature of fragmenting atomic clusters can been extracted from the initial kinetic energies of ionic products. To improve the accuracy of the temperature measurements, we have designed an ionic velocity map imaging spectrometer with high kinetic energy resolution. Firstly, based on the simulations using Simion8.0 software, the high resolution is obtained by adjusting the structure of the electrostatic lenses and collimation of molecular beam. According to theoretical analysis, it is proved that the spectrometer has a well defined kinetic energy resolution. Then, we have studied the delay ionization processes of C₆₀ induced by nanosecond laser. A series of narrowed two-dimensional time-sliced velocity images of the C₆₀⁺ with increasing the delayed time were recorded. Analysis revealed that Coulomb force between C₆₀⁺ clusters in same laser shots will broadening the transverse distribution of 2D image. Considering the influence of Coulomb force on initial kinetic energy of C₆₀⁺ clusters, the high resolution has been proved by analysing the negative relationship between Coulomb force and delayed time. It indicates that the establishment of the spectrometer builds up a good basis for next experiments on the studies for molecular thermodynamics in atomic clusters.

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Reference (23)

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Velocity Map Imaging Spectrometer for Studying the Atomic Cluster Thermodynamics

doi: 10.11804/NuclPhysRev.33.04.506

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