Browsing by Author "Hosseini, S."

Now showing 1 - 4 of 4

Neutral dissociation of hydrogen molecules in a strong laser field through superexcited states
(2011-04-28)
Azarm, A.
;
Song, D.
;
Liu, K.
;
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.
;
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
Population trapping and rotational revival of N(2) molecules during filamentation of a femtosecond laser pulse in air
(2010-12-14)
Azarm, A.
;
Ramakrishna, S.
;
Talebpour, A.
;
Hosseini, S.
;
Teranishi, Y.
We study the fluorescence emitted from filaments in air using a pump-probe scheme with a femtosecond Ti-sapphire laser. The fluorescence intensities from the first negative band (B(2)Sigma(+)(u) -> X(2)Sigma(+)(g)) and the second positive band (C(3)Pi(u) -> B(3)Pi(g)) show enhancement and change periodically as a function of the pump-probe time delay. We attribute this phenomenon to the universal yet probably forgotten phenomenon of population trapping of nitrogen molecules in highly excited states together with field-induced alignment of nitrogen molecules followed by revivals of the rotational wavepackets. Theoretical calculation of the alignment dynamics of nitrogen molecules is consistent with the experimental data.
Population trapping and rotational revival of N-2 molecules during filamentation of a femtosecond laser pulse in air
(2010-12-14)
Azarm, A.
;
Ramakrishna, S.
;
Talebpour, A.
;
Hosseini, S.
;
Teranishi, Y.
We study the fluorescence emitted from filaments in air using a pump-probe scheme with a femtosecond Ti-sapphire laser. The fluorescence intensities from the first negative band (B-2 Sigma(+)(u) -> X-2 Sigma(+)(g)) and the second positive band (C-3 Pi(u) -> B-3 Pi(g)) show enhancement and change periodically as a function of the pump-probe time delay. We attribute this phenomenon to the universal yet probably forgotten phenomenon of population trapping of nitrogen molecules in highly excited states together with field-induced alignment of nitrogen molecules followed by revivals of the rotational wavepackets. Theoretical calculation of the alignment dynamics of nitrogen molecules is consistent with the experimental data.