Eierman S, Peng Z, Calvin A, Brzeczek M, Satterthwaite L, Patterson D
Department of Physics, University of California, Santa Barbara, California 93106, USA.
Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA.
Rev Sci Instrum. 2023 Jul 1;94(7). doi: 10.1063/5.0147695.
We report on an ion trapping system for performing a novel form of cryogenic messenger spectroscopy with single molecule sensitivity. The system features a cryogenic radio-frequency ion trap loaded with single analyte molecules via a quadrupole mass filter. We demonstrate the ability to controllably attach inert gas particles to buffer gas cooled, trapped molecular ions. Sympathetic cooling by co-trapped, laser cooled 88Sr+ further reduces the translational temperature of trapped molecules to the millikelvin regime. We verify the presence of cryogenic "tags" via non-destructive optical mass spectrometry and selectively remove these adducts by resonantly driving vibrational transitions in the tagged molecular ions. This enables us to derive the vibrational spectrum of a single analyte molecule from the frequency dependence of the tag detachment rate. We have demonstrated these capabilities by measuring transitions in the C-H stretching region for single cationic fragments of both indole (C8H7N) and 1,3-benzodioxole (C6H4O2CH2). These capabilities are not reliant on a specific molecular level structure and thus constitute a general, non-destructive method for vibrational spectroscopy of individual molecular ions.
我们报道了一种用于进行具有单分子灵敏度的新型低温信使光谱学的离子捕获系统。该系统的特点是一个低温射频离子阱，通过四极质量过滤器加载单个分析物分子。我们展示了可控地将惰性气体颗粒附着到缓冲气体冷却、捕获的分子离子上的能力。通过共捕获的激光冷却的88Sr+进行的交感冷却进一步将捕获分子的平动温度降低到毫开尔文范围。我们通过非破坏性光质谱法验证低温“标签”的存在，并通过共振驱动标记分子离子中的振动跃迁选择性地去除这些加合物。这使我们能够从标签分离速率的频率依赖性中得出单个分析物分子的振动光谱。我们通过测量吲哚（C8H7N）和1,3-苯并二恶唑（C6H4O2CH2）的单个阳离子片段在C-H伸缩区域的跃迁来证明了这些能力。这些能力不依赖于特定的分子水平结构，因此构成了一种用于单个分子离子振动光谱学的通用、非破坏性方法。
