Baba Masaaki, Saitoh Motohisa, Taguma Kunio, Shinohara Keisuke, Yoshida Kazuto, Semba Yosuke, Kasahara Shunji, Nakayama Naofumi, Goto Hitoshi, Ishimoto Takayoshi, Nagashima Umpei
Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
J Chem Phys. 2009 Apr 7;130(13):134315. doi: 10.1063/1.3104811.
Rotationally resolved ultrahigh-resolution spectra of the S(1) (1)B(2u)<--S(0) (1)A(g) transition of anthracene-h(10) and anthracene-d(10) have been observed using a single-mode UV laser and a collimated supersonic jet. We have determined rotational constants of the zero-vibrational levels of the S(0) and S(1) states by analyzing the precisely calibrated transition wavenumbers of rotational lines. We measured Zeeman splitting of each rotational line in the external magnetic field, of which the magnitude was small and strongly dependent on the rotational quantum numbers. We have shown that the magnetic moment in the S(1) (1)B(2u) state arises from J-L coupling with the S(2) (1)B(3u) state and that mixing with the triplet state is negligibly small. We concluded that the main radiationless transition in the S(1) state of anthracene is not intersystem crossing to the triplet state but internal conversion to the ground state. We also examined methods of ab initio theoretical calculation to determine which method most closely yielded the same values of rotational constants as the experimentally obtained ones. Moller-Plesset second-order perturbation method with a 6-31G(d,p) basis set yielded approximately the same values for the S(0) (1)A(g) state with an error of less than 0.04%. Geometrical structure in the S(0) (1)A(g) state of the isolated anthracene molecule has been accurately determined by this calculation. However, configurational-interaction with single excitations, time-dependent Hartree-Fock, and time-dependent density-function-theory methods did not yield satisfactory results for the excitation energy of the S(1) (1)B(2u) state. Symmetry-adapted-cluster configuration-interaction calculation was sufficiently good for the excitation energy and rotational constants.
使用单模紫外激光和准直超声速射流，观测到了蒽 - h₁₀和蒽 - d₁₀的S(1) (¹B₂ᵤ)←S(0) (¹A₉)跃迁的转动分辨超高分辨率光谱。通过分析转动谱线精确校准的跃迁波数，我们确定了S(0)和S(1)态零振动能级的转动常数。我们测量了外部磁场中每条转动谱线的塞曼分裂，其大小较小且强烈依赖于转动量子数。我们已经表明，S(1) (¹B₂ᵤ)态的磁矩源于与S(2) (¹B₃ᵤ)态的J - L耦合，并且与三重态的混合小到可以忽略不计。我们得出结论，蒽S(1)态的主要无辐射跃迁不是系间窜越到三重态，而是内转换到基态。我们还研究了从头算理论计算方法，以确定哪种方法能最接近地给出与实验获得的转动常数相同的值。采用6 - 31G(d,p)基组的莫勒 - 普莱塞二阶微扰法给出的S(0) (¹A₉)态值大致相同，误差小于0.04%。通过该计算精确确定了孤立蒽分子S(0) (¹A₉)态的几何结构。然而，单激发组态相互作用、含时哈特里 - 福克和含时密度泛函理论方法对于S(1) (¹B₂ᵤ)态的激发能并未给出令人满意的结果。对称适配团簇组态相互作用计算对于激发能和转动常数足够好。
