Intracavity laser absorption spectroscopic investigation of barium desorption from dispenser cathodes

Intracavity laser absorption spectroscopy was used to measure the number density of neutral ground state barium atoms desorbed from an operating dispenser cathode. The measurement suggests an order of magnitude value of 10⁸ atoms/cm³ at a distance of 5 cm from the emitting surface. This is the first direct state selective measurement of the barium density near to the surface of an operating cathode which can be directly traced to conventional multipass absorption spectroscopy. The value we obtain is consistent with results reported by other workers using less direct methods and allows more detailed statements to be made concerning the chemical state of the Ba at the instant of desorption.