以Nd:YAG雷射四倍頻266 nm或三倍頻355 nm光解，氙燈為偵測光源來偵測2,3-diphenyl-8,9-dihydro-6H-8λ4-[1,2]oxathiino[4,5-g]quinoxalin-8-one（DPQXS,35） 所得吸收光譜波形相類似，吸收峰位於310、390及450 nm，過了550 nm仍有一寬廣且吸收度小的吸收帶，在330-370 nm則有photon-bleaching現象。吸收峰所偵測的吸收衰減皆為雙指數衰減，且不同吸收波長擬合所得生命期相近。短生命期在乙腈中的生命期為270 ns，正己烷為160 ns、甲苯為170 ns。長生命期以390 nm的吸收擬合所得在乙腈中的生命期為3.9 ms，正己烷中為0.8 ms、甲苯中為1.2 ms。在極性高的溶劑中有生命期較長的現象。以266 nm雷射光解，以fumaronitrile、N-phenylmaleimide及氧為淬熄劑的淬熄速率分別為上限107 M-1s-1，1.9 × 108 M-1s-1，2.5× 109 M-1s-1。由氧氣淬熄速率極快加上ESR光譜偵測得三重態雙自由基訊號，推測DPQXS光解後產生三重態雙自由基。由吸收衰減光譜可得知在吸收之前有一極快的放光，以超快雷射系統配合光子計數偵測技術可得此放光亦為雙指數衰減，生命期分別為100 ps及5 ns。配合動力學計算可知100 ps為跨系統穿越（intersystem crossing）完成的時間，5 ns為三重態能態的生命期。到達三重態後SO2脫去產生三重態雙自由基，和臨菎雙烯產生平衡反應，因此偵測到雙指數衰減。由不同溫度所測生命期作Arrhenius圖可得短及長生命期所對應活化能分別為(31±1) kJ/mol及(61±7) kJ/mol。此二活化能代表雙自由基和臨菎雙烯平衡反應的活化能或雙自由基和臨菎雙烯其餘衰減反應所需克服活化能，則需進一步實驗證實。此實驗結果符合當初對sultine分子的假設，光解可脫去SO2以產生雙自由基或臨菎雙烯以用於有機合成等應用。

The transient absorption spectra of 2,3-diphenyl-8,9-dihydro-6H-8λ4-[1,2]oxathiino[4,5-g]quinoxalin-8-one (DPQXS, 35) in various solvent after photolysis at 266 nm or 355 nm are recorded. For both photolysis wavelengths the transient absorption spectra of produced intermediate display similar features with absorption maximum at 310, 390 and 450 nm. A weak broad feature at wavelength longer than 550 nm is also observed. All measured absorption curves display similar bi-exponential decay. The lifetime of the fast component in solvent acetonitrile, n-hexane and toluene is 270, 160 and 170 ns and the slow one is 3.9, 0.8 and 1.2μs, respectively. The quenching rates for the transient species measured for quencher fumaronitrile, N-phenylmaleimide and oxygen are 107M-1s-1, 1.9´108 M-1s-1and 2.5´109 M-1s-1, respectively. Because quenching rate of oxygen is efficient we conclude that the transient product is a triplet biradical. From the obtained Arrhenius plot, the activation energy of fast and slow process is (31±1) kJ/mole and (61±7) kJ/mole. The dissociation mechanism of DPQXS upon excitation in the UV region proposed to undergo fast intersystem crossing to the triplet manifold. Dissociation occurs in the triplet surface for formation the triplet products. Therefore, the transient absorption spectrum is assigned to the triplet biradical form of o-quinodimethane.

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