Department of Chemistry, University of California, Davis, California 95616, USA.
J Chem Phys. 2013 May 7;138(17):174309. doi: 10.1063/1.4803161.
Two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser photoionization and pulsed field ionization-photoelectron (PFI-PE) study of gaseous titanium monoxide (TiO) in the total energy range of 55,000-57,320 cm(-1) has been conducted. The TiO molecules were selectively excited to single J' rotational levels of the intermediate TiO*(B(3)Π1, ν' = 0) state by using a VIS dye laser and then ionized by using another UV laser. This two-color photoexcitation method has allowed the measurement of cleanly J(+)-resolved PFI-PE spectra for the TiO(+)(X (2)Δ(5/2,3/2); v(+) = 0, 1, and 2) vibrational bands. By simulating the rotationally resolved PFI-PE spectra, J(+) = 3∕2 is determined to be the lowest rotational level of the ground electronic state, confirming that the symmetry of the TiO(+) ground state is (2)Δ(3/2). Irregular intensity patterns for rotational PFI-PE peaks that deviated from the regular patterns that favor the rotational transitions with small change of the core rotational angular momentum, are observed. This observation is indicative of strong perturbations of the PFI-PE rotational transitions, possibly by a channel-coupling mechanism. The analysis of the PFI-PE spectra yields highly precise values for the adiabatic ionization energy of TiO [IE(TiO) = 55 005.4 ± 0.8 cm(-1) (6.81980 ± 0.00010 eV)], and the vibrational frequency (ωe(+) = 1056.1 ± 0.8 cm(-1)), the anharmonicity constant (ωe(+)χe(+) = 4.4 ± 0.8 cm(-1)), the rotational constants (B(e)(+) = 0.5613 ± 0.0009 cm(-1) and αe(+) = 0.0029 ± 0.0008 cm(-1)), and the equilibrium bond length (r(e)(+) = 1.583 Å) for the TiO(+)(X (2)Δ(3/2)) ground state, the vibrational frequency (ωe(+) = 1058.4 ± 0.8 cm(-1)), the anharmonicity constant (ωe(+)χe(+) = 5.1 ± 0.8 cm(-1)), the rotational constants (B(e)(+) = 0.5715 ± 0.0007 cm(-1) and αe(+) = 0.0030 ± 0.0004 cm(-1)) and the equilibrium bond length (r(e)(+) = 1.568 Å) for the excited spin orbit state TiO(+)(X (2)Δ(5/2)), along with the spin-orbit coupling constant (A = 105.9 ± 0.2 cm(-1)) for TiO(+)(X (2)Δ(5/2,3/2)).
我们在 55000-57320cm^-1 的总能量范围内，对气态一氧化钛（TiO）进行了双色可见-紫外（VIS-UV）共振增强激光光解和脉冲场电离-光电（PFI-PE）研究。通过使用可见染料激光将 TiO 分子选择性激发到中间 TiO*（B（3）Π1，ν'=0）态的单个 J'转动能级，然后用另一个 UV 激光使其离子化。这种双色光激发方法允许测量 TiO+（X（2）Δ（5/2，3/2）；v+=0，1 和 2）振动带的清晰 J（+）分辨 PFI-PE 光谱。通过模拟旋转分辨 PFI-PE 光谱，确定 J（+）=3∕2 是基态的最低转动能级，证实 TiO（+）基态的对称性为（2）Δ（3∕2）。观察到偏离有利于核转动角动量变化较小的转动跃迁的规则模式的不规则 PFI-PE 峰的强度模式。这种观察表明 PFI-PE 转动跃迁受到强烈的微扰，可能通过通道耦合机制。PFI-PE 光谱的分析给出了 TiO 绝热电离能的高度精确值[IE（TiO）=55005.4±0.8cm^-1（6.81980±0.00010eV）]，以及振动频率（ωe（+）=1056.1±0.8cm^-1），非谐性常数（ωe（+）χe（+）=4.4±0.8cm^-1），转动常数（B（e）（+）=0.5613±0.0009cm^-1 和αe（+）=0.0029±0.0008cm^-1），以及 TiO（+）（X（2）Δ（3/2））基态的平衡键长（r（e）（+）=1.583Å），振动频率（ωe（+）=1058.4±0.8cm^-1），非谐性常数（ωe（+）χe（+）=5.1±0.8cm^-1），转动常数（B（e）（+）=0.5715±0.0007cm^-1 和αe（+）=0.0030±0.0004cm^-1）和激发自旋轨道态 TiO（+）（X（2）Δ（5/2））的平衡键长（r（e）（+）=1.568Å），以及 TiO（+）（X（2）Δ（5/2，3/2））的自旋轨道耦合常数（A=105.9±0.2cm^-1）。
