Precision Spectroscopy with Single Polyatomic Molecules

我们通过研究分子如何吸收和发射光(光谱学)来了解分子的结构和量子力学性质。几乎所有的光谱都是在含有许多分子的样品上进行的。这些大样本会产生很大的信号，但它们有一个缺点--所测量的一切实际上都是样本的平均值。例如，一些分子移动得很快，一些分子移动得很慢，一些分子在旋转，等等。这种变化限制了分子测量的精确度。在这项工作中，由本科生和研究生组成的研究团队以及首席研究员将使用新的、非常灵敏的技术来测量单分子。该团队将非常精确地测量这些单分子--事实上，这些测量将是有史以来对由两个以上原子组成的分子进行的最精确的测量。在未来，这种精确度将使科学家能够使用这种分子来寻找超出我们目前理论设想的新物理。这项研究为加州大学圣巴巴拉分校的研究生和本科生提供了具有挑战性的动手研究项目。作用光谱学是一种能够测量分子离子振动光谱的通用技术。最近在~10K的分子系综上展示了一种新的、功能强大的作用光谱--漏出光谱。这种方法已经产生了分辨率约为100 MHz的多普勒受限振动光谱。加州大学圣巴巴拉分校的研究小组将把这项技术推广到毫克尔文温度下的单分子区域，然后扩展到兰姆-迪克区域，该区域没有表现出一阶多普勒频移。这将在千赫范围内提供分辨率，并将首次实现广泛的多原子分子离子的高精度光谱，包括手性分子离子。这项技术在寻找新的物理和纳米分析化学方面有应用。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

We learn a great deal about the structure and quantum mechanical nature of molecules by studying how they absorb and emit light (spectroscopy). Almost all spectroscopy is done on samples containing many molecules. These large samples give large signals, but they come with a disadvantage - everything that is measured is actually an average value of the sample. For example, some molecules are moving fast, some are moving slowly, some are spinning, and so on. This variety limits the precision with which the molecules can be measured. In this work, the research team of undergraduate and graduate students and the principal investigator will use new, very sensitive techniques which can measure single molecules. The team will measure these single molecules very precisely - in fact, these measurements will be the most precise measurements ever made of molecules that are composed of more than two atoms. This precision will, in the future, allow scientists to use such molecules to search for new physics beyond that envisioned in our current theories. This research provides challenging, hands-on research projects for graduate and undergraduate students at the University of California, Santa Barbara.Action spectroscopy is a versatile technique capable of measuring the vibrational spectra of molecular ions. A new, powerful version of action spectroscopy, leak out spectroscopy, has recently been demonstrated on ensembles of molecules at temperatures of ~10 K. This method has yielded Doppler-limited vibrational spectra with resolution of about 100 MHz. The research team at the University of California, Santa Barbara will extend this technique, first into the single molecule regime at millikelvin temperatures, and then to the Lamb-Dicke regime, which exhibits no first order Doppler shift. This will give a resolution in the kHz regime, and will for the first time enable high-precision spectroscopy of a broad range of polyatomic molecular ions, including chiral molecular ions. The technique has applications in searches for new physics and nano-analytic chemistry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.