DETERMINATION OF THE ABSOLUTE EXCITED-STATE DENSITY OF A SODIUM TARGET BY MEANS OF BEAM DEFLECTION MEASUREMENTS

The average deflection of a laser excited, divergent sodium beam with a broad velocity distribution is measured by means of a Langmuir-Taylo r detector and exploited for determining the absolute density of the e xcited state in the interaction area. Simulations of the excitation an d deflection process point out that the knowledge of the velocity dist ribution of the sodium atoms plays a crucial part in obtaining reliabl e information from deflection measurements. From the comparison of sim ulated and experimental results we find that in our set-up typically 3 0% of the sodium atoms are in the excited state when both ground state levels are pumped with an intensity of 35 mW cm-2 from an electro-opt ically modulated CW laser beam; the corresponding excited state densit y is 1.5 x 10(9) cm-3.