Sample interview questions: Explain the concept of laser-induced fluorescence and its applications in atomic physics research.
Sample answer:
Laser-induced fluorescence (LIF) is a powerful technique used in atomic physics research to study the energy levels and dynamics of atoms and molecules. It involves the excitation of atoms or molecules to higher energy levels using laser light, followed by the subsequent emission of fluorescence as the excited states decay back to lower energy levels. This emitted fluorescence contains valuable information about the atomic or molecular system under investigation.
There are several key components involved in the process of laser-induced fluorescence. Firstly, a laser source is used to generate high-intensity, monochromatic light of a specific wavelength. The choice of wavelength is crucial as it needs to correspond to an energy transition that can excite the atoms or molecules of interest. The laser light is then directed towards the sample, which typically contains a dilute gas or a vapor of the atomic or molecular species being studied.
When the laser light interacts with the atoms or molecules in the sample, it can be absorbed, leading to the excitation of the system to higher energy levels. The excited atoms or molecules are in a temporary, unstable state and will rapidly decay back to lower energy levels. During this decay process, they emit fluorescence, which is typically at a longer wavelength than the absorbed laser light. The emitted fluorescence is collected and analyzed to extract valuable information about the atomic or molecular system.
The applications of laser-induced fluorescence in atomic physics research are extensive and diverse. One significant application is in the study of energy levels and spectra of atoms and molecules. By precisely controlling the laser wavelength, researchers can selectively excite specific energy levels and observe the resulting fluorescence. This allows for the determination of energy level structures, quantum states, and transition probabilities of atomic and molecular species.