Experimental studies on the determination of the dipole moments of some different laser dyes

In this paper we used the Stokes shift phenomena to determine the difference in the dipole moments of the excited state mu(e) and ground state mu(g) to be (mu(e) - mu(g)), and the polarizability alpha. In this paper, we studied six different laser dyes belonging to four different classes of laser dyes which are diolefin 2,5-Distyryl pyrazine (DSB); 1,4-Bis (-pyridyl-2-vinyl) benzene (P2VB) and p-Bis-(o-methylstyryl)-benzene (Bis-MSB) with (mu(e) - mu(g)) equal to 6.40, 6.70 and 2.98 Debye, respectively; anthracene class includes 10(4-acetoxyphenyl)-2-methyl-9-acetoxy anthracene (APMAA) with (mu(e) - mu(g)) value of 7.25 Debye; Rhodamine B (RB) with (mu(e) - mu(g)) value of 5.33 Debye; and Coumarin 120 (C120) with the value 3.97 Debye for (mu(e) - mu(g)). In addition the value of both polarizability alpha and the radius r of each investigated laser dye molecule are determined. Therefore. the ratio alpha/r(3) for each dye is calculated to be 0.93, 0.79, 0.39, 0.37, 0.67 and 0.76 for DSP, P2VB, Bis-MSB, APMAA, RB and C120. respectively. The values of r are 4.83, 4.83, 4.90, 5.34, 5.75 and 4.11 Angstrom for the above consequence laser dyes. These dyes are studied in a large number of different solvents. The values obtained of (mu(e) - mu(g)) for these selected dyes are positive, which means that the excited state is more polar than the ground state. (C) 2003 Elsevier B.V. All rights reserved.