A vacuum ultraviolet photolysis of ethyl bromide at 147 nm was studied over the pressure range of 0.5-50 Torr at room temperature, using a Xenon resonance lamp. The pressure effect with and without He as an additive was investigated. As a collision partner $C_2H_5Br$ was found to be more effective than He in energy transfer. A scavenger effect of the reaction was also observed by adding NO as a radical scavenger. The extinction coefficient of $C_2H_5Br$ at 147 nm and 298 K was found to be 712 ± 7 $atm^{-1} cm^{-1}$.
The principal reaction products were $CH_4, C_2H_2, C_2H_4$, and $C_2H_6$. Increasing pressure, the product quantum yields, Ø , of $CH_4$ (Ø =0.019 ± 0.004) and $C_2H_4$ (Ø = 0.57 ± 0.01) remain constant, while that of $C_2H_2$ (Ø =0.03 to 0) was found to be weak negative pressure dependence, and that of $C_2H_6$ (Ø =0.39 to 0.43) was weak positive pressure dependence. Addition of NO completely suppressed the formation of $C_2H_2$ and $C_2H_6$, and partially reduced that of $C_2H_4$ (Ø = 0.50 ±0.01). These results were interpreted in terms of two channel competition between the molecular eliminations and the formation of radicals. And their contributions to the decomposition are approximately half-and-half.
From the aforementioned results, it seems to be reasonable to assume that there exist two electronically excited states. One state which is initially formed plays a role as the main source of the molecular elimination products. And the other state resulted from the first excited state by collisional cross over goes on the radical decomposition modes.
147 nm 의 광을 내는 크세논 램프를 이용하여 에틸 브로마이드의 광분해 반응을 0.5 - 50 Torr 의 시료 압력 범위에서 행하였다. 주생성물로 메탄, 아세틸렌, 에틸렌, 그리고 에탄이 확인됐다. 첨가물로서 헬륨을 넣고 실험한 결과, 에틸 브로마이드가 헬륨에 비해 에너지 전달 효율이 더 좋음을 알았다. 라디칼 스케빈져로서 NO 를 첨가했을 때는 오직 에틸렌만 생성되었다.
반응 생성물 분포에 대한 압력 효과와 스케빈져 효과가 면밀히 분석되었다. 그 결과, 에틸 브로마이드의 광분해 반응에는 두 가지 들뜬 상태가 관여함을 알았다. 첫번째 들뜬 상태는 초기에 Rydberg 형 전이에 의해 생겨, HBr 분자 이탈 반응을 일으키거나 충돌에 의하여 다른 들뜬 상태로 전이한다. 충돌에 의하여 생긴 두번째의 들뜬 상태에서는 탄소와 브롬 사이의 결합을 끊는 반응이 주로 일어난다. 이와 같이 서로 다른 들뜬 상태에 의해 일어나는 분자 이탈 반응과 라디칼 생성 반응의 비율이 각각 50% 임을 알았다.
