Organic scintillators with unusually large Stokes' shifts

Abstract

Publication costs assisted by Kernforschungszentrum KarlsruheA series of methyl and/or methoxy substituted 1,3-diphenyl-2-pyrazolines were synthesized for evaluation as solutes in liquid scintillation counting systems. The electronic absorption spectra, absolute fluorescence spectra, fluorescence quantum yield, fluorescence decay times, as well as the relative pulse height of 15 1,3-diphenyl-2-pyrazolines were measured in benzene at room temperature. Unusually large Stokes' shifts with high fluorescence quantum yields of about 0.90 are obtained when bulky methyl and/or methoxy substituents are attached in ortho, ortho' positions of the phenyl rings in 1 and/or 3 positions of the 2-pyrazoline ring. The sterically hindered 1,3-diphenyl-2-pyrazolines have a promising potential as scintillators for liquid scintillation counting. Due to the large Stokes' shift the highly soluble sterically hindered 1,3-diphenyl-2-pyrazolines can be used as primary solutes without requiring a wavelength shifter.

Spectroscopy of electron-induced fluorescence in organic liquid scintillators

“…As no significant contribution appears above ∼ 500 nm, it can be concluded that there is no evidence for phosphorescence in the measured spectra. PMP displays a broad and less structured fluorescence spectrum which has also been reported in the literature [19].…”

The next-generation liquid-scintillator neutrino observatory LENA

“…The fluor PMP [27] is a primary solute with a large Stokes shift of about 120 nm, resulting in a marginal overlap of the absorption and emission spectra and thus a small self-absorption. The primary fluor PPO has a Stokes shift of ∼60 nm and is therefore usually used in combination with a secondary fluor, Bis-MSB.…”

Photochemical mechanisms producing large fluorescence stokes shifts

“…Figure 4 shows capillary measurements of the fluorescence loss through reabsorption as a function of the distance de. The perylimid-based dye B-241, discussed for fluorescent solar concentrators due to its extremely high photostability and its fluorescence quantum yield of unity [28], has been compared to 3HF, an ESIPT compound with a large Stokes shift, and to PMP, one of the most widespread scintillator dyes [18].…”