MEASUREMENT OF SODIUM DENSITY AND THE NA 514-NM TRANSITION-PROBABILITY IN A HIGH-PRESSURE SODIUM ARC

Spatially resolved arc temperatures and sodium density measurements are presented for two high-pressure sodium arcs. Absolute intensities of the optically thick 818/819-nm lines were used to determine the arc temperature while the radial profile of the optically thin 514-nm line was Abel inverted to determine the Na atomic density. Agreement with an independent measurement of the Na density obtained by controlling pressure of sodium in the lamp with a tin bath consistently required a value for the Na 514-nm transition probability 2-3 times smaller than the literature value (A=0.011×108 s -1) of Wiese, Smith, and Miles [Atomic Transition Probabilities, NSRDS-NBS 4 (NBS, Washington, DC, 1971), Vol. II], obtained from quantum mechanical calculations. The results of three separate experiments indicate that the value should be modified to A=0.0040×108 s-1 with a standard deviation of ±21%. A more detailed error analysis including systematic error would indicate an accuracy to within ±33%.