Plat© 1] A b so rp tio n sp e c tra of lo w -pressure flam es A bsorption sp ectra o f low-pressure flam es, w h ich h a v e a rela tiv ely th ick reaction zone, h ave been stu d ied b y m eans o f a m ultiple-reflexion sy stem t o increase th e effective p a th len gth in th e flam e gases. To ob tain a background source o f sufficient brightness tem perature to reverse the absorption bands, a flash tu b e and rotatin g sector d evice has been em ployed . F or a rather rich o x y a c ety len e

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... flam e, th e (0, 0) Sw an band o f C2 and th e 3143 A ban d o f CH h ave been observed in absorption for th e first tim e in ste a d y flam es. A valu e for th e reversal tem p era ture o f C2 has been obtained. R ich -lim it low-pressure flam es o f ethers and aldehyd es show form aldehyde absorption. In rich flam es o f d im eth y l ether, acetald eh yd e, aceton e and m eth ane, a ban d o f th e CH 3 radical a t 2157 A has been observed, and in flam es o f d ieth y l ether, and o f eth an e, a new ban d w ith m axim a a t 2220 and 2242 A is p rovision ally assigned to th e C2H 6 radical. The absorption b y O H and OD radicals in flam es o f m ixed C2D 2 + H 2 h ave been exam in ed . R esu lts are discussed. 21 [ 323 ] Vol. 256. A.