N2O在60-120nm之吸收光譜、光游離與螢光激發光譜; the absorption and fluorescence excitation spectrum of N2O in the 60-130 nm wavelength region

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题名:	N2O在60-120nm之吸收光譜、光游離與螢光激發光譜;the absorption and fluorescence excitation spectrum of N2O in the 60-130 nm wavelength region
作者:	楊和蓉;He-Rong Yang
贡献者:	化學研究所
关键词:	吸收光譜;螢光激發光譜;一氧化二氮;fluorescence;FES;photoionization;photoabsorption;N2O
日期:	2011-08-25
上传时间:	2012-01-05 14:29:25 (UTC+8)
摘要:	摘要本實驗利用新竹同步輻射中心(NSRRC)穩定的同步輻射光源(SR) 測量N2O在 60-130nm 波長範圍的吸收以及螢光激發光譜。Seya光束線(4B1解析度: 0.015-0.13 nm))是用來測量吸收光譜(ABS)，另外使用High-Flux(3A1,解析度: 0.04-0.075nm))研究螢光激發光譜(FES) 。螢光訊號是因為N2O被電離或光解後的激發態所產生的。兩隻光電管,分別收集由N2O+( 2Σ+, 2Π, 2Π+)及其他中性分子激發後所產生在175-320 nm (Hamamatsu R1460) 及180-650 nm (EMI 9789QB)的螢光輻射訊號。吸收光譜(ABS)在100-130 nm方面，本實驗吸收數值與Shaw23等(1992)做比較，吸收值略為高一些。在69-100 nm方面，本實驗與Shaw23等(1992)有類似的結果，但在吸收截面積方面有些微差異(本實驗小約10-20%)。在60-96nm範圍內吸收光譜存在幾個雷德堡態系列的吸收，分別為收斂至 2Π(2π-1,12.886eV; 96.2 nm), 2Σ+(7σ-1, 16.388eV, 75.64 nm ), 2Π(1π-1,17.65 eV, 70.24 nm ), 2Π+ (7σ-1,20.105eV, 61.66 nm)。螢光部份份為三部份探討: (1)在入射波長74-80nm的範圍，螢光激發光譜主要為收斂至N2O+ 2Σ+雷德堡態，與Ukai24等(1994)的 FES 結果類似，螢光主要貢獻來自ndπ和nsσ 雷德堡系列。由於N2O+ 2Σ+在300-420nm皆會放射螢光，FES是由非雷德堡態N2O+( 2Σ+→ 2Π)所產生的螢光，N2O+ ( 2Σ+→ 2Π1/2)的振動模式為(0,0,0) →(0,0,0)與(1,0,0) →(0,0,0)皆有明顯的躍遷，波長位置分別為355.85與339.55nm。(2).而在入射波長69-75nm區間，FES為雷德堡態收斂至N2O+ 2Π，光譜有明顯的vibrational progression結構，且隨著波長變小而強度減弱，另外N2O+ ( 2Σ+→ 2Π1/2)的螢光激發光譜，在此區同樣有vibrational progression結構，但不隨波長變化而變化。(3) 在入射波長60-69nm間，FES主要為收斂至N2O+ 2Π+的ndπ和nsσ系列雷德堡態，但是在本區域中npπ系列，呈現窗口共振(window resonance)式結構，它們是直接自游離所造成。在N2O+( 2Σ+→ 2Π)螢光激發光譜當中，結果類似Lee 16(1977)，且我們的光譜解析（0.04nm）度比Lee16所量測光譜還要好。 abstract In this experiment, we have employed synchrotron radiation of NSRRC as the light source to study the absorption and fluorescence excitation of N2O in the 60-130 nm wavelength region. The beam line SEYA (4B1) with a resolution of 0.015-0.13 nm and the High Flux (3A1) with a resolution of 0.04-0.075nm have been used for measuring the absorption(ABS) and fluorescence excitation spectra (FES) experiments. Fluorescence signals were measured by using two photomultiplier tubes (EMI 9789QB, Hamamatsu R1460 for emissions produced by the excited states N2O+( 2Σ+, 2Π, 2Π+) and other neutral emissions. In the wavelength region 100-130 nm, our experimental results are compared with Shaw23. In 69-100 nm , our absorption spectrum are generally agreeable with the the spectra of Shaw et al23 (1992)with small difference in the absolute cross sections. In 60-96 nm, absorption spectrum are assigned to a few Rydeberg states convering to 2Π(2π-1, 12.886eV), 2Σ+(7σ-1,16.388eV), 2Π(1π-1,17.65 eV), 2Π+ (7σ-1,20.105eV). The FES experiments are discussed in three wavelength regions as follows: (1) In 74-80 nm, FES are produced by Rydberg states converging to N2O+ 2Σ+ which are comparable to previous works of Ukai et al.24(1992). In this wavelength region fluorescence produced in 175-320 nm are mainly contributed by Rydberg states ndπ and nsσ converging to N2O+( 2Σ) . Between 300-420 nm, there are vibrational levels (0,0,0) and (1,0,0) of the N2O+ 2Σ+ excited states. (2) In the wavelength region 69-75 nm, FES are mainly produced by vibrational levels of the excited states N2O+( 2Π) and weakly of N2O+( ). The intensity of N2O+( 2Π) decreases while shorter wavelength irradiation, but intensity of N2O+( ) is independent with wavelength. （3） In 60-69 nm, there are mainly ndπ and nsσ series converging to N2O+ 2Π+ with FES also contributed by N2O+( 2Σ+→ 2Π) showing window resonances observed for npπ series. Our results are compared with Lee et al.16 (1977) but with better resolution.
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