研究目的
To resolve discrepancies in the assignment of electronic transitions of dibenzo-p-dioxin (DD) by providing additional experimental evidence through synchrotron radiation linear dichroism (SRLD) spectroscopy.
研究成果
The study provided polarization data for DD by SRLD polarization spectroscopy, leading to the observation of four long-axis and three short-axis polarized major features. The results demonstrated the usefulness of LD spectroscopy in the assignment of electronic transitions to molecular states, suggesting revision of previous assignments. The observed polarization directions led to experimental symmetry assignments of the observed transitions, with the experimental spectra well predicted by TD-DFT calculations.
研究不足
The high-energy region of the spectrum is very complex, with broad and overlapping long- and short-axis polarized band systems, making assignment of observed features to calculated electronic transitions tentative. The TD-DFT procedure may be less reliable in the high-energy region.
1：Experimental Design and Method Selection:
SRLD spectroscopy on molecular samples aligned in stretched polyethylene was used to investigate the UV absorption spectrum of DD.
2：Sample Selection and Data Sources:
A sample of DD was purchased from TCI Europe n.v. (purity >99%). Low-density polyethylene (PE) was used as the alignment medium.
3：List of Experimental Equipment and Materials:
Synchrotron radiation source at the CD1 beamline at ISA, stretched polyethylene, chloroform, ethanol.
4：Experimental Procedures and Operational Workflow:
DD was introduced into PE from a saturated solution in chloroform, followed by evaporation and stretching of the PE sample. SRLD spectra were measured with the electric vector of the sample beam parallel and perpendicular to the stretching direction.
5：Data Analysis Methods:
The observed spectra were analyzed using the Trial and Error Method (TEM) for orientation factors and compared with theoretical transitions predicted by TD-DFT calculations.
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