Browsing by Author "Song, D."

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Direct observation of super-excited states in methane created by a femtosecond intense laser field
(2008-11-28)
Azarm, A.
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Xu, H. L.
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Kamali, Y.
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Bernhardt, J.
;
Song, D.
We report, for the first time, a direct observation of the super-excited states of CH(4) in femtosecond intense laser fields using a pump (800 nm)-probe (1338 nm) technique. An unambiguous depletion of the CH (A (2) Delta -> X (2)Pi) fluorescence signal as a function of the delay time is attributed to the de-excitation of the super-excited states by the probe laser pulse. The lifetime of the super-excited state is measured to be about 160 fs.
Highly Multiphoton Excitation of Molecule by Intense Laser Field
(2009)
Teranishi, Y.
;
Hayashi, M.
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Song, D.
;
Azarm, A.
;
Kong, F.
Multiphoton excitation of molecule by intense laser field is studied theoretically to explain the recent experiments of neutral fragmentation Neutral fragments are created from highly excited parent molecule Excitation mechanism is discussed with the use of Floqet theory.
Neutral dissociation of hydrogen molecules in a strong laser field through superexcited states
(2011-04-28)
Azarm, A.
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Song, D.
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Liu, K.
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Hosseini, S.
;
Teranishi, Y.
Fragmentation of hydrogen molecules in a strong laser field is studied experimentally and theoretically. Balmer lines (n -> 2) from hydrogen atoms are observed up to n = 14. The emission intensity of the two strongest Balmer lines versus laser intensity in a log-log plot gives a slope of more than 11. This indicates that some high-lying states in the continuum are excited resulting in neutral dissociation. Adapting Rydberg state approximation, the potential energy curves of superexcited states of hydrogen are plotted. Semi-empirical calculation confirms dissociation through these superexcited states. The upper limit of the lifetime of the superexcited states is obtained by an ultrafast pump and probe experiment by monitoring one of the fluorescence lines.
Neutral dissociation of simple molecules in strong laser field
(2011)
Azarm, A.
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Song, D.
;
Teranishi, Y.
;
Hosseini, S.
;
Lin, S. H.
we report neutral dissociation of simple molecules in strong laser field, experimentally. Moreover, theoretical calculations of potential energy curves justify neutral dissociation through super excited states in all of the investigated gases. (C) 2010 Optical society of America
Studying the neutral dissociation of O-2 and CH4 Molecules in strong laser field
(2009)
Azarm, A.
;
Kamali, Y.
;
Bernhardt, J.
;
Xu, H. L.
;
Song, D.
We report neutral dissociation of oxygen and methane in femtosecond laser field through superexcited states. Moreover, the lifetime of the superexcited state is measured by pump and probe technique to be about few hundred femtosecond. (C)2009 Optical Society of America