2014 Fiscal Year Annual Research Report
| Project/Area Number |
14F04333
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| Research Institution | The University of Tokyo |
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Principal Investigator |
山内 薫 東京大学, 理学(系)研究科(研究院), 教授 (40182597)
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| Co-Investigator(Kenkyū-buntansha) |
SZIDAROVSZKY Tamas 東京大学, 理学(系)研究科(研究院), 外国人特別研究員
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| Project Period (FY) |
2014-04-25 – 2017-03-31
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| Keywords | dihydrogen-helium cation / intense laser field / nuclear dynamics / photodissociation / charge transfer |
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| Outline of Annual Research Achievements |
The first goal of our research (starting from 2014.10.14.) is to theoretically investigate the dynamics of the H_2He+ molecular ion when exposed to an intense laser field.
Nuclear dynamics of the molecule was investigated on its ground electronic state in the absence of external field. Extensive amounts of electronic structure calculations were carried out to construct the three potential energy surfaces and 10 dipole moment surfaces needed to describe laser-matter interaction. Reduced-dimensional wavepacket propagation simulations were carried out to investigate the nuclear dynamics of the molecule, when exposed to an intense femtosecond laser pulse in the visible range.
The results obtained are rich and exciting. It was found that: 1) H_2He+ exhibits only 16 bound vibrational, and an overall 411 bound (ro)vibrational states. 2) Both excited PESs are involved in the laser-matter interaction, and a large variety of photodissociation products are produced. 3) The H_2He+ molecule dissociates to much lesser extent than H_2+ in the same conditions. 4) Kinetic coupling between vibrational degrees of freedom has a large effect on the wavepacket dynamics, thus on the dissociation product yields. 5) After fast initial dissociation processes, slow decay is observed along the H-He coordinate (along which dissociation can undergo at low energy) via vibrational energy redistribution from the highly excited H-H mode. 6) Highly excited vibrational states of H_2He+ are produced.
Based on the scientific results obtained, a manuscript is currently being prepared for publication.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Our plan was to simulate the full-dimensional rovibrational dynamics of H_2He+ in an intense laser field. Although the presence of an unexpected third potential energy surface in the system complicated the situation, I managed to carry out theoretical simulations in a simplified model and observe a great variety of interesting scientific results.
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| Strategy for Future Research Activity |
There seems to be two logical ways to continue on with our research at this point.
1) Simulations show that if longer wavelength laser light is used to excite the H_2He+ molecule (800 nm instead of 400 nm), the third potential energy surface seems to play very little role in the photo induced dynamics. Therefore, for such cases it could be sufficient to use only two potential energy surfaces (neglecting intersections and avoided crossings in order to have a simple functional form) and full-dimensional rovibrational simulations might be attempted.
2) The validity of the linear H_2He+ model parallel to the laser polarization axis was only addressed in a qualitative manner so far, therefore, it would be useful to describe quantitatively the spatial alignment of H_2He+ through polarization interaction with a lower intensity external field. This could be done by using the field-free bound (ro)vibrational states as a basis set, which were already computed previously.
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