Observing molecular structures by using high-order harmonic generation in mixed gases

Abstract

We demonstrate that the structure of ${\mathrm{CO}}_{2}$ molecules can be determined by measuring the phases of harmonics from them. This is evidenced by observing a phase jump of harmonics generated in a mixed gas of aligned ${\mathrm{CO}}_{2}$ molecules and their reference Kr atoms, which serve to extract the net contribution due to the structure of ${\mathrm{CO}}_{2}$ molecules. Furthermore, in the strong field approximation model, we derive the exact conditions of quantum interference during high-order harmonic generation in ${\mathrm{CO}}_{2}$ molecules analytically and we propose a method to control harmonic pulse duration.