ABSTRACT
In this paper we used the Stokes shift phenomena to determine the difference in the dipole moments of the excited state micro(e) and ground state micro(g) to be (micro(e)-micro(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 (micro(e)-micro(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 (micro(e)-micro(g)) value of 7.25 Debye; Rhodamine B (RB) with (micro(e)-micro(g)) value of 5.33 Debye; and Coumarin 120 (C120) with the value 3.97 Debye for (micro(e)-micro(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 A for the above consequence laser dyes. These dyes are studied in a large number of different solvents. The values obtained of (micro(e)-micro(g)) for these selected dyes are positive, which means that the excited state is more polar than the ground state.
