What is emitted when the laser interacts with a cell at the interrogation point?

When a laser interacts with a cell at the interrogation point, the primary outcome is the emission of photons. This occurs because the excitation energy from the laser light causes certain molecules within the cell to emit light as they return to their ground state. These emitted photons are what the photomultiplier tube (PMT) or photodetector (PD) captures and converts into a measurable electronic signal.

The detection of photons is crucial for various cytometric analyses, as the characteristics of the emitted light—such as its intensity and wavelength—can provide valuable information about the cell's properties, including size, granularity, and specific surface markers. This data is then used to analyze and differentiate between various cell types within a sample, making the role of photon emission and detection central to the functioning of flow cytometry.

Understanding this interaction is fundamental for interpreting the data produced in cytometric applications, as the quality and characteristics of the emitted photons directly influence the accuracy and reliability of the results obtained.