The most populated structure of tetrahydrofuran(THF)has been investigated in our previous study~(17)using electron momentum spectroscopy(EMS).Because of the relatively low impact energy(600 eV)and low energy resolution(DELTA E=1.20 eV)in the previous experiment,only the highest occupied molecular orbital(HOMO)of THF was investigated.The present study reports the most recent high-resolution EMS of THF in the valence space for the first time.The binding energy spectra of THF are measured at 1200 and 2400 eV plus the binding energies,respectively,for a series of azimuthal angles.The experimentally obtained binding energy spectra and orbital momentum distributions(MDs)are employed to study the orbital responses of the pseudorotation motion of THF.The outer valence Greens function(OVGF),the OVGF/6-311++G** model,and density function theory(DFT)-based SAOP/et-pVQZ model are employed to simulate the binding energy spectra.The orbital momentum distributions(MDs)are produced using the DFT-based B3LYP/aug-cc-pVTZ model,incorporating thermodynamic population analysis.Good agreement between theory and experiment is achieved.Orbital MDs of valence orbitals exhibit only slight differences with respect to the impact energies at 1200 and 2400 eV,indicating validation of the plane wave impulse approximation(PWIA).The present study has further discovered that the orbital MDs of the HOMO in the low-momentum region(p<0.70 a.u)change significantly with the pseudorotation angle,,giving a v-shaped cross section,whereas the innermost valence orbital of THF does not vary with pseudorotation,revealing a very different bonding mechanism from the HOMO.The present study explores an innovative approach to study pseudorotation of sugar puckering,which sheds a light to study other biological systems with low energy barriers among ring-puckering conformations.
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机译：在我们先前的研究中（17），我们使用电子动量谱（EMS）研究了四氢呋喃（THF）的人口最多的结构。由于相对较低的冲击能（600 eV）和较低的能量分辨率（DELTA E = 1.20 eV）在先前的实验中，仅研究了THF的最高占据分子轨道（HOMO）。本研究首次报道了价态空间中THF的最新高分辨率EMS。一系列方位角分别为1200和2400 eV加上结合能。通过实验获得的结合能谱和轨道动量分布（MDs）研究THF伪旋转运动的轨道响应。外价格林函数（OVGF），OVGF / 6-311 ++ G **模型和基于密度泛函理论（DFT）的SAOP / et-pVQZ模型来模拟结合能谱。产生轨道动量分布（MDs）使用基于DFT的B3LYP / aug-cc-pVTZ模型，结合了热力学人口分析。理论和实验之间取得了良好的一致性。价轨道的轨道MDs在1200和2400 eV处的冲击能仅表现出细微的差别，表明平面波的有效性本研究进一步发现，低动量区域（p <0.70 au）中HOMO的轨道MD随伪旋转角显着变化，给出v形横截面，而THF的最内价轨道不随伪旋转而变化，揭示了与HOMO完全不同的键合机理。本研究探索了一种创新的方法来研究糖皱褶的伪旋转，这为研究其他低能垒的生物系统提供了启示。皱褶构象。
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