Specific features of the generation of aqueous solutions of Rhodamine 6G in laser pumping

Dual fluorescence and laser emissions from fluorescein-Na and eosin-B

“…Generally, at higher concentration, quenching of fluorescence from monomeric species takes place mainly due to the inactive absorption of the exciting light by non-luminescent aggregates, as well as due to the migration of energy of electronic excitation from monomers to such aggregates. However, as reported for the case of Rh-6G dye [7,[28][29][30], dimers of the present dyes can participate effectively in the formation of stimulated emission both by monomers and dimers. Since the emission spectra of dimers are not separated from those of monomers, the generation efficiency cannot be estimated.…”

“…In this context, it should be noted that the aggregates of rhodamine 6G dye molecules formed at high concentration have been reported to participate in the lasing process [7]. Generally, at high concentrations, the dye molecules come nearer together by random motion, and they interact with one another either by coulombic force of attraction and/or H-bonding depending on the species involved.…”

“…Simultaneous lasing at distinct regions, though well known in mixed dyes via energy transfer mechanisms, is rarely observed in a single component dye. Studies on dual dye lasers from coumarin, 9-aminoacridine and rhodamine dyes have been reported by Masilamani et al [6], Akimov et al [7] and Hammond and Hughes [8], and the lasings were attributed to two emitting species, one normal form and the other TICT conformation and molecular associates, and molecular exciplex, respectively. We report in this paper, for the first time, the observation of dual laser emissions from ethanolic solutions of fluorescein-Na and eosin-B in a narrow concentration range under N 2 laser excitation.…”

“…For example, acridine orange in organic glasses and in EtOH at 77 K [22,23], rhodamine dyes Rh-6G [7], Rh-19 [24], and Rh-B [25] in ethanolic and aqueous solutions, Cresyl Violet in water [26] form aggregates. For fluorescein-Na, in alkaline aqueous solutions at 1 Â 10 À1 mol dm À3 , dimeric species has been reported [21].…”