Wright Adam D, Nelson Jane C, Weichman Marissa L
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
J Chem Phys. 2023 Oct 28;159(16). doi: 10.1063/5.0170326.
Cavity coupling of gas-phase molecules will enable studies of benchmark chemical processes under strong light-matter interactions with a high level of experimental control and no solvent effects. We recently demonstrated the formation of gas-phase molecular polaritons by strongly coupling bright ν3, J = 3 → 4 rovibrational transitions of methane (CH4) to a Fabry-Pérot optical cavity mode inside a cryogenic buffer gas cell. Here, we further explore the flexible capabilities of this infrastructure. We show that we can greatly increase the collective coupling strength of the molecular ensemble to the cavity by increasing the intracavity CH4 number density. In doing so, we can tune from the single-mode coupling regime to a multimode coupling regime in which many nested polaritonic states arise as the Rabi splitting approaches the cavity mode spacing. We explore polariton formation for cavity geometries of varying length, finesse, and mirror radius of curvature. We also report a proof-of-principle demonstration of rovibrational gas-phase polariton formation at room temperature. This experimental flexibility affords a great degree of control over the properties of molecular polaritons and opens up a wider range of simple molecular processes to future interrogation under strong cavity-coupling. We anticipate that ongoing work in gas-phase polaritonics will facilitate convergence between experimental results and theoretical models of cavity-altered chemistry and physics.
气相分子的腔耦合将能够在强光与物质相互作用下对基准化学过程进行研究，实现高水平的实验控制且无溶剂效应。我们最近通过将甲烷（CH₄）明亮的ν₃、J = 3→4振转跃迁与低温缓冲气体池内的法布里 - 珀罗光学腔模式进行强耦合，证明了气相分子极化激元的形成。在此，我们进一步探索该实验装置的灵活性能。我们表明，通过增加腔内CH₄数密度，可以大幅提高分子系综与腔的集体耦合强度。在此过程中，我们可以从单模耦合 regime 调谐到多模耦合 regime，其中随着拉比分裂接近腔模间距，会出现许多嵌套的极化激元态。我们探索了不同长度、精细度和镜面曲率半径的腔几何结构下的极化激元形成。我们还报告了室温下振转气相极化激元形成的原理验证演示。这种实验灵活性为分子极化激元的性质提供了高度控制，并为未来在强腔耦合下进行更广泛的简单分子过程研究开辟了道路。我们预计，气相极化激元学的持续研究将促进腔改变的化学和物理实验结果与理论模型之间的融合。
