Ask AI: Explain the working principle of a hollow cathode lamp and references? 2. Explain the operation of a photomultiplier tube(PMT) and references?

1. Hollow Cathode Lamp Working Principle: A hollow cathode lamp (HCL) is a type of discharge lamp primarily used in atomic absorption spectrophotometry. It typically consists of a cathode, an anode, and a noble gas sealed together in a glass tube. The cathode is often made from the element that the lamp is designed to produce, usually metals such as copper, silver, or magnesium. When a voltage is applied between the anode and the cathode, the gas inside the tube gets ionized, which in turn causes the metal atoms in the cathode to get excited. As these excited atoms return to their ground state, they emit light at a specific wavelength, characteristic of the metal used. This light is then typically directed out of the lamp and into a spectrometer, which measures the wavelength and intensity of the absorbed light, providing information of the analyte in the sample. References: - Hollas J. M., (2004) Modern spectroscopy, (4thedn), John Wiley & Sons, Ltd. - Spectroscopy: Hollow Cathode Lamps, University of Bristol, School of Chemistry. 2. Photomultiplier Tube Operation: A photomultiplier tube (PMT) is a device used to detect and amplify light. It operates on the principle of photoelectric effect, where a single incident photon strikes a photosensitive surface, causing the emission of an electron. This initial electron (photoelectron) is then accelerated by an electric potential towards a series of secondary electrodes (dynodes), each at a more positive potential than the last. When the primary photoelectron strikes the first dynode, it causes the emission of multiple secondary electrons. This process, known as secondary emission, is repeated at each dynode thereby resulting in an avalanche of electrons. This electron multiplication process gives the PMT its high gain and makes it a sensitive detector for light, capable of detecting single photons. The PMT’s output is a current, hence, the larger the number of incident photons at the entrance of the PMT, the higher the output current. References: - Knoll, Glenn F. (2010) "Radiation Detection and Measurement," 4th edition. - Hamamatsu, Photomultiplier Tubes: Basics and Applications, 3rd edition.