266 nm光解碘化甲烷類分子之可見光區放射光譜研究

Visible Wavelength Emission Spectroscopy Following the 266 nm Photolysis of Iodomethanes

楊欣樺(Sin-hua Yang)

指導教授 ： 張伯琛

國立中央大學/理學院/化學系/碩士(2011年)

摘要

我們以266 nm石榴石雷射光 (Nd：YAG laser) 於流動式樣品槽 (slow flow cell) 中光解二碘甲烷 (CH2I2) 與碘甲烷 (CH3I) ，先前本實驗室研究結果顯示光解碘化甲烷類分子在可見光區有一系列未知譜帶。在本研究中搭配高靈敏度增強式電荷偶合偵測器 (High Sensitivity Intensified Charge-Coupled Device Detector) 獲得訊雜比 (S/N ratio) 改進至少三倍且完整掃瞄由近紅外光區到可見光區之未知譜帶初始放射光譜 (nascent emission spectrum) ，藉由觀察譜線的頻率位置、強度分布、頻寬大小及波形作為分析這些譜帶之依據，同時比較不同壓力下、不同延遲時間下之實驗。分析結果顯示這些未知譜帶之放射光譜可能是由同一上能階放射至不同下能階，其下能階之振動結構頻率ω1為434.9±0.6 cm-1，ω2為220±3 cm-1，我們因而推論可能之分子即可能之光解機制。

關鍵字

碘化甲烷類分子 ； 光解 ； 初始放射光譜

並列摘要

266 nm laser photolysis of CH2I2 and CH3I were conducted in a slow flow cell. Previous results show that this photolysis produces several unknown bands in the nascent emission spectrum at visible wavelengths. In this study, a high sensitivity intensified charge-couple device (ICCD) detector was employed for recording better nascent emission spectra from near-infrared to visible wavelengths with the improvement on signal-to-noise ratios of at least a factor of 3. Frequencies, bandwidths, and waveforms of these unknown bands provide the data basis for analysis. Emission spectra under different pressures and those at different delay times were also acquired. These results indicate that the unknown bands are a series of emission bands that originate from the same upper level to different lower levels. The ground state vibrational parameters are determined to be: ω1= 434.9±0.6 cm-1 and ω2= 220±3 cm-1. The possible carrier molecule of these unknown bands could be therefore identified.

並列關鍵字

iodomethanes ； photolysis ； nascent emission spectrum

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