激發態氧原子與一氧化碳同位素交換反應之動態學研究

Abstract

本篇論文利用交叉分子束的方式，來研究激發態氧原子與一氧化碳同位素交換的反應動態學，其觀察的碰撞能量為5.56千卡每莫耳。實驗的結果觀察到兩個反應途徑:一個是由激發態氧原子放熱到基態氧原子的過程；另外一個則是保持在激發態氧原子，但能量由動能轉換成振動能量或轉動能量。實驗的結果發現，兩個反應途徑中，以保持在激發態氧原子的途徑為主，占了全部反應的百分之六十六；同時，實驗結果也發現產物的角分佈是呈現不對稱的形狀，這樣的角分佈形狀透露出反應會形成中間產物，而它的半生期跟它的轉動週期比起來相對較短，才會產生不對稱的角分佈。另一個反應則相反，激發態氧原子藉由放熱到基態氧原子的過程，為副反應占全部反應的百分之三十四，其結果顯示出產物的角分佈是對稱的，其對稱的角分佈形狀透露出，反應所形成的中間產物它的半生期與它的旋轉週期比起來相對較長，才會產生對稱的角分佈，我們稱這樣的中間產物為長壽的中間產物。

The dynamics of the 18O(1D) + 28CO oxygen isotope exchange reaction has been studied using a crossed molecular beam apparatus at a collision energy of 5.56 kcal/mol. Two reaction channels are observed: isotope exchange in which quenching to O(3P) occurs and isotope exchange in which the product oxygen atom remains on the singlet surface. Non-quenching channel is the major channel with asymmetry angular distribution under this collision energy, accounting for 66% of all isotope exchange. The other channel occurs quenching which angular distribution is symmetric accounts for 34%. The electronic quenching proceeds via a CO2* complex that is long-lived with respect to its rotational period; however, non-quenching channel proceeds via CO2* complex with the lifetime is shorter than its rotational period. The new molecular-level details may help provide a more quantitative understanding of the heavy isotope enrichment in CO observed in the stratosphere.