Photophysical properties and laser performance of photostable UV laser dyes. Part 1. Substituted p-quaterphenyls

Abstract

In the bulk gas, the rp(O) value monotonically changes from about 200 to 100 ns with increasing excitation energy (Table I). These values agree fairly well with the fluorescence lifetimes obtained in the supersonic jet.11,12 Accordingly, the slow fluorescence in the bulk gas obviously corresponds to the fluorescence which shows a single exponential decay in the jet. In the bulk gas also, the fast component is very difficult to detect in the decay curve for 338.7-nm excitation (see Figure 6a). However, the molecular level structure even at a very low vibrational level of St cannot be identified as the small molecule limit. As already mentioned, the minute analysis of the experimental results on the quantum yield and decay of the fluorescence at various pressures in the bulk gas indicates that the fluorescence characteristics of acetaldehyde vapor for region-I excitation belong to the intermediate case.The electronic relaxation in St of acetaldehyde vapor after region-I excitation is thus characterized by reversible intersystem crossing to T¡. The Sj -* T, intersystem crossing yield in lower vibrational levels of Si acetaldehyde was reported by Gandini and Hackett5 to be unity at moderately high pressures. Therefore, the lifetime of the fast fluorescence can reasonably be related to the T¡ intersystem crossing rate. The possibility, suggested by Noble and Lee,11•12 that isolated acetaldehyde molecules excited to lower vibrational levels in Sj undergo internal conversion to S0 may be ruled out.Noble and Lee11,12 suggested further that the fast fluorescence, observed in a bulk gas by Atkinson et al.,9 is to be emitted from levels with considerably high rotational quantum numbers. As mentioned previously, however, both the quantum yield and the decay of fluorescence seem to be almost independent of the rotational level excited. It is, therefore, very improbable that the fast component which can be observed in a bulk gas corresponds to fluorescence from high rotational levels.

Dye-Loaded Zeolite L Sandwiches as Artificial Antenna Systems for Light Transport

“…The extinction coefficient of 1,2-bis(5-methyl-benzoxazol-2-yl)-ethene (MBOXE) in ethanol was reported to be e (362 nm,EtOH) 4.3 Â 10 4 L mol À1 cm À1 . [56] Pyronine (Py) with acetate and oxonine (Ox) with perchlorate as counter ion were synthesized and purified according to the procedures described in the literature. [26,57,58] The extinction coefficients of pyronine (e max 8.3 Â 10 4 L mol À1 cm À1 ) reported by Müller [57] and oxonine (e max 7.8 Â 10 4 L mol À1 cm À1 ) reported by Vogelmann [59] were used in all subsequent measurements.…”

“…[26,57,58] The extinction coefficients of pyronine (e max 8.3 Â 10 4 L mol À1 cm À1 ) reported by Müller [57] and oxonine (e max 7.8 Â 10 4 L mol À1 cm À1 ) reported by Vogelmann [59] were used in all subsequent measurements. The fluorescence quantum yields and the natural lifetimes of the dyes used in the sandwich materials are F DPH,MeOH 0.27/t DPH,MeOH 19.3 ns, [55] F MBOXE,EtOH 0.78/t MBOXE,EtOH 1.5 ns, [56] F Py,EtOH % 1/t Py,EtOH 3.2 ns, [60] F Ox % 1/t Ox,EtOH 3.5 ns. [59] 1-Butanol (Fluka, for UV spectroscopy, > 99.8 %) was used as solvent without further drying.…”

Cyclic Ether Auxofluors on Oligophenylene Laser Dyes

“…Placement of t-butyl groups on the outer meta positions of quaterphenyl gives a dye with fairly high output, but very short lifetime. 4 Sulfonation of quaterphenyl produces a dye, "polyphenyl 1", which is soluble only in viscous solvents, and apparently suitable only for low power outputs. 6 Attempts to promote solubility with alkoxy groups on the meta and para positions of the outer phenyl rings has little effect on solubility unless the groups are large,2 as in the most successful ultraviolet-emitting dye in current use--BBQ, dye 10 ( Figure 4).…”

“…5 Placement of alkoxy groups on either the outer meta positions or any internal ortho positions gives dyes with very short lifetimes. 4 For some time we have sought a way to extend the useful range of the laser emission of oligophenylene laser dyes beyond the ultraviolet into the visible. Such a red-shift in the emission spectrum would require the attachment of auxofluors along the main axis of the oligophenylene to extend the conjugation of.…”

“…Equally high FQE, high energy output as a laser dye, and good lifetime when XeCI* laser pumped was reported for 3,3'"-dimethylquaterphenyl. 4 Terminal methoxy groups on a quaterphenyl gave good lasing lifetime when flashlamp pumped, 5 while the branched alkyl groups in dye 10 did not. Para-methoxyalkylarenes were very resistant to reaction with oxygen at 100, t5 certainly a desirable feature in a laser dye.…”