Schlaghaufer Florian, Slenczka Alkwin
Institute for Physical and Theoretical Chemistry, University of Regensburg, Regensburg, Germany.
Phys Chem Chem Phys. 2022 Sep 14;24(35):20921-20931. doi: 10.1039/d2cp02256g.
Spectroscopic investigation of phthalocyanine in the gas phase has tremendously profited from molecular beam spectroscopy. Isentropic expansion succeeds in reducing the population of rovibrational states to the vibrational ground state so that only low energy rotational states remain populated. However, with respect to UV-vis spectroscopy the pioneers of molecular beam spectroscopy came to the discouraging conclusion that the information contained in the rotational structure of a large molecule is minimal, and even if the rotational structure could be resolved with great effort, the results are unlikely to be worth the difficulty [Levy, , 1980, 197-225]. Just over 4 decades later we would like to announce that the result is worth the effort, indeed. Even without full line resolution, the rotational structure at the electronic band origin of phthalocyanine provides deep insight into configurational details of phthalocyanine for both electronic states. These details serve as gas phase compliment to the investigation of microsolvation in superfluid helium droplets. To the best of our knowledge this is the largest molecule ever analyzed by means of its rotational degrees of freedom.
气相中酞菁的光谱研究极大地受益于分子束光谱学。等熵膨胀成功地将振转态的布居数降低到振动基态，使得只有低能量的转动态仍有布居。然而，对于紫外可见光谱学而言，分子束光谱学的先驱们得出了令人沮丧的结论，即大分子转动结构中包含的信息极少，而且即使付出巨大努力能够解析转动结构，结果也不太可能值得如此困难[利维，1980，197 - 225]。仅仅40多年后，我们想要宣布结果确实值得付出努力。即使没有完全的谱线分辨率，酞菁电子能带起源处的转动结构也能深入洞察酞菁两种电子态的构型细节。这些细节作为气相补充，用于超流氦滴中的微溶剂化研究。据我们所知，这是通过其转动自由度分析的最大分子。
