Threshold dependence of the vibrational excitation of molecules on laser radiation intensity |
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Authors: | G Yu Grigor’ev L I Men’shikov P L Men’shikov Sh Sh Nabiev |
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Institution: | 1.Russian Research Center Kurchatov Institute,Moscow,Russia |
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Abstract: | The collisionless vibrational excitation of a polyatomic molecule in an IR laser radiation field has been theoretically studied. It has been shown that (i) the degree of vibrational excitation (namely, number 0000 of vibrational quanta of a molecular mode near-resonant with the IR laser field that are absorbed by the molecule) is low if laser pulse intensity P (energy flux density in the laser beam) is lower than a certain critical value P cr; (ii) the degree of excitation abruptly increases after crossing the boundary where P = P cr; (iii) this effect is attributed to two properties inherent in polyatomic molecules, namely, the anharmonicity of the vibrational mode interacting with the laser field and the energy exchange with other modes; and (iv) at P > P cr, number 00000 is determined only by energy density Φ = PτP, where τP is the laser pulse duration, 00000 monotonically increases with increasing Φ. The model is in good agreement with the experimental data. |
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