苯甲酸晶体中氢键二聚体的6 ~ 293 K中子衍射研究和宏观量子理论
A neutron diffraction study from 6 to 293 K and a macroscopic-scale quantum theory of the hydrogen bonded dimers in the crystal of benzoic acid
摘要：
苯甲酸晶体由互变异构的中心对称二聚体通过双氢键连接而成。从6 K到293 K的中子衍射排除了成键质子的统计无序。除了衍射数据，振动光谱和弛豫率测量与固态核磁共振和准弹性中子散射是一致的，而不是粒子状质子。我们提出了一个宏观尺度的量子理论为代表的周期晶格的费米子的成键质子。绝热分离、不相容原理和反对称假设产生了一个不受退相干影响的静态晶格态。根据量子测量的理论，振动光谱学和弛豫测量涉及到测量之前不存在的非局域对称物种的无消相干布洛赫态的实现。本征态完全由三个与温度无关的参数决定，这些参数是有效测量的：互变异构体子晶格之间的能量差;质子振子的双阱不对称性;波函数的离域度。布洛赫态的自发衰变解释了弛豫数据。另一方面，由弹性散射实现的静态占衍射数据。我们得出结论，量子和经典物理在任何温度下都成立。
英文摘要：
The crystal of benzoic acid is comprised of tautomeric centrosymmetric dimers linked through bistable hydrogen bonds. Statistical disorder of the bonding protons is excluded by neutron diffraction from 6 K to 293 K. In addition to diffraction data, vibrational spectra and relaxation rates measured with solid-state-NMR and quasi-elastic neutron scattering are consistent with wave-like, rather than particle-like protons. We present a macroscopic-scale quantum theory for the bonding protons represented by a periodic lattice of fermions. The adiabatic separation, the exclusion principle, and the antisymmetry postulate yield a static lattice-state immune to decoherence. According to the theory of quantum measurements, vibrational spectroscopy and relaxometry involve realizations of decoherence-free Bloch states for nonlocal symmetry species that did not exist before the measurement. The eigen states are fully determined by three temperature-independent parameters which are effectively measured: the energy difference between tautomer sublattices; the double-well asymmetry for proton oscillators; the delocalization degree of the wavefunctions. The spontaneous decay of Bloch states accounts for relaxometry data. On the other hand, static states realized by elastic scattering account for diffraction data. We conclude that both quantum and classical physics hold at every temperature.
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