Abstract: A system for measuring velocities and densities of a particle-free flow of molecules is provided. In various embodiments of the disclosure, the system may include a laser configured to form a two-dimensional light sheet for interrogating a flow of molecules at a measurement region with the two-dimensional light sheet. The system may include a first camera coupled with a first filter and a second camera coupled to a second filter. The cameras can be oriented toward the measurement region at a first angle and a second angle, respectively, with respect to a direction of the two-dimensional light sheet. The cameras are configured to capture images of scattered light from the measurement region through the filters. The two-dimensional spatial distribution of density and velocity values of the flow of molecules can be determined based on the images acquired via the first camera and the second camera.