Molecular Beam Experiments for the Physical Chemistry Laboratory

物理化学实验室将开发使用分子束探索气体动力学理论和温度概念的新实验。该项目将建造一个相对简单的装置，能够产生脉冲和超音速光束。主要的实验将使用飞行时间方法来直接验证热束中分子速度的麦克斯韦-玻尔兹曼分布。通过检查一系列气体并使用计算机辅助拟合他们的数据，学生们将能够验证速度分布与分子质量和温度的关系。作为该实验的延伸，操作条件将被修改以使波束变为超音速。这导致了非热的速度分布，在这种分布中，束分子不能通过温度来适当地表征。对这种分布的观察将引导学生思考温度的物理意义。该项目展示了物理化学中重要的经典思想，同时使学生接触到现代仪器和技术。

New experiments using a molecular beam to explore the kinetic theory of gases and the concept of temperature will be developed for the physical chemistry lab. A relatively simple apparatus, capable of producing both effusive and supersonic beams, will be constructed for the project. The principal experiment will use time of flight methods to directly verify the Maxwell-Boltzmann distribution of molecular speeds in a thermal beam. By examining a series of gases and using computer aided fitting of their data, students will be able to verify the dependence of the speed distribution on molecular mass and temperature. As an extension of this experiment, the operating conditions will be modified so that the beam becomes supersonic. This leads to a nonthermal speed distribution in which the beam molecules are not properly characterized by a temperature. Observation of this distribution will lead students to consider the physical meaning of temperature. The project provides a demonstration of important classical ideas in physical chemistry while at the same time exposing students to modern instrumentation and techniques.