Methods of Experimental Physics, Volume 3: Molecular Physics focuses on molecular theory, spectroscopy, resonance, molecular beams, and electric and thermodynamic properties. The manuscript first considers the origins of molecular theory, molecular physics, and molecular spectroscopy, as well as microwave spectroscopy, electronic spectra, and Raman effect. The text then ponders on diffraction methods of molecular structure determination and resonance studies. Topics include techniques of electron, neutron, and x-ray diffraction and nuclear magnetic, nuclear quadropole, and electron spin resonance. The publication takes a look at mass spectrometry and molecular beams, including molecular structural applications, chemical kinetics, beam formation and detection, molecular beam optics, and spectroscopy. The text also considers the electric properties of molecules and ultrasonic studies and thermodynamic properties of fluids. The manuscript is a dependable reference for readers interested in molecular physics.