Abstract: The Maxwell-Boltzmann velocity distribution law serves as a fundamental principle in statistical physics and chemical kinetics. Its experimental verification spanned over a century, during which numerous sophisticated measurement techniques were developed. This paper comprehensively examines three pivotal experimental approaches: mechanical velocity selection, force-field deflection, and time-offlight measurements. The mechanical velocity selection method confirmed the validity of the distribution law, while the force-field deflection technique, employing both magnetic and gravitational deflection, provided independent verification and systematically characterized the perturbations in molecular beam velocity distributions caused by oven collisions. The time-of-flight method progressed from qualitative observations to contemporary high-precision measurements, extending its applications to diverse complex systems and revealing non-ideal distribution characteristics in practical beam sources. These complementary methodologies not only established a robust experimental foundation for the Maxwell-Boltzmann velocity distribution law but also significantly advanced our understanding of molecular beam dynamics from equilibrium to non-equilibrium states, thereby contributing substantially to modern surface science and materials preparation technologies.

Key words: Maxwell-Boltzmann distribution, Velocity distribution, Molecular beam, Mechanical velocity selector, Time-of-flight method