研究目的
Investigating the motion of electrons in atoms, molecules and solids on attosecond timescales, particularly focusing on the state-resolved probing of attosecond timescale molecular dipoles in iodomethane.
研究成果
The study reveals light-induced couplings of core-excited states in molecules in a state-resolved manner, demonstrating that the state-specific induced dipole response to a moderately intense NIR field is strongly dependent on the dipole coupling to nearby states. The findings pave the way to observing ultrafast intra-molecular dynamics with excellent time and energy resolution.
研究不足
The study is limited by the short lifetimes of the core-hole states, making it difficult to observe couplings with standard two-photon spectroscopies. Additionally, the broadness of the interference fringes due to the high density of Rydberg states might hide clearly identifiable light-induced structures (LIS).
1：Experimental Design and Method Selection:
The study employed attosecond transient absorption spectroscopy (ATAS) to investigate the induced-dipole response of iodomethane (CH3I) molecules. The methodology involved the use of a moderately intense, non-ionizing NIR field and an XUV attosecond pulse train (APT), with their relative phase controlled.
2：Sample Selection and Data Sources:
The experiment focused on the electronic excitation around 50.6 eV and 52.3 eV from the iodine 4d5/2 and 4d3/2 semi-core levels to the lowest unoccupied molecular orbital (LUMO) σ* in CH3I.
3：6 eV and 3 eV from the iodine 4d5/2 and 4d3/2 semi-core levels to the lowest unoccupied molecular orbital (LUMO) σ* in CH3I.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Few-cycle 800 nm wavelength laser pulses with a duration of 6 fs (FWHM) at 1 kHz repetition rate were used for both providing the NIR field and obtaining XUV pulses by HHG in argon. The NIR pulses were characterized by the SEA-F-SPIDER technique.
4：Experimental Procedures and Operational Workflow:
XUV-only and XUV+NIR absorption spectra of CH3I were measured in quick succession by using a chopper wheel to modulate the NIR beam. The delay between the XUV and NIR pulses was scanned over 28 fs in 0.2 fs steps.
5：2 fs steps.
Data Analysis Methods:
5. Data Analysis Methods: The absorbance was calculated from the single atom response via the Beer-Lambert law, taking into account the estimated gas density and interaction length. The simulations were averaged over 600 orientations of CH3I and over 8 uniformly distributed values of the CEP within 0 and 2π.
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