本研究於室溫下流動式樣品槽中光解碘化甲烷類分子(二碘甲烷、碘仿及氯碘甲烷)，在先前研究中發現在560 nm-820 nm有一系列未知譜帶，經由同位素實驗得知為只含碘的物種。我們以532 nm雷射激發碘分子B3Π+0,u←X1Σ+g之螢光分光光譜與未知譜帶比對後得知未知譜帶主要即為碘分子B-X放射，而此碘分子主要為雷射光解碘化甲烷類分子產生碘原子經碰撞後產生，再經雷射激發至B state後放光產生未知譜帶，為一多光子過程。分析532 nm激發碘分子B←X躍遷之螢光分光光譜發現並非單一上能階之放射光譜，其光譜之上能階振動量子數(v′)主要為33與36。我們偵測未知譜帶之放射生命期會受碘化甲烷類分子碰撞而明顯地淬息，成功地解釋先前觀測未知譜帶放射生命期只有約170 ns的原因。我們以不同雷射波長光解CH2I2發現分解第一個C-I鍵所需的能量為208 ±2 kJ/mol。 We have recorded nascent emission spectra following the photolysis of iodomethanes (CH3I, CH2I2, and CH2ICl). Our previous study has observed a series of unknown bands in the region from 560 nm to 820 nm, and confirmed that the carrier of these unknown bands contains no carbon or hydrogen atoms. The dispersed fluorescence spectrum of exciting the I2 B3Π+0,u←X1Σ+g transition at 532 nm was acquired and was found to be very similar to the unknown bands, and this verifies the dominant structure of the unknown bands to be the I2 B→X emission. We also found that the observed I2 mostly comes from the collisions between iodine atoms generated from the photolysis of iodomethanes. A laser excitation following the formation of I2 pumps molecular iodine to its B state whose emission bands constitute of the unknown bands. This is a multiphoton process. Furthermore, our new result also shows that the unknown bands are dominated by the emission from the B state v′= 33 and 36 levels instead of a single vibrational level in the previous study. We have also observed the I2 B state quenching by the iodomethanes, and this successfully explain the previous observed 170 ns emission lifetime of unknown bands. Moreover, I2 emission spectra following the photolysis of CH2I2 at different wavelengths were recorded and the threshold energy for breaking the C-I bond in CH2I2 is determined to be 208 ±2 kJ mol-1.
