有自吸收现象时谱线强度与物质浓度的关系

谱线强度(I)与物质浓度(C)之间的定量关系是定量光谱分析的物理基础。由于实际光源中的谱线或多或少地都有自吸收现象,所以在实际情形下,I与C的关系是较为复杂的。本文中应用迁移取样法进行铸铁中的硅的光谱分析,选择了适当的条件,使Si 2516多重谱线系中的Si 2519线在光源中不发生自吸收,因而可以用它的强度代表光源中的物质浓度,同时测定了多重谱线系中发生自吸收最严重的Si 2516线的定标曲线斜度b与物质浓度C的关系(b=klogC+β+1),从而得出I与C的关系式如下:logI=k/2(logC)²+(β+1)logC+α,这里β与α是试验条件下的两个常数;k是b与logI₂₅₁₉的关系直线的斜度。在理想的情形,当谱线没有自吸收时,b=1,k=0,所以logI与logC之间便有直线的关系;当谱线有自吸收时,谱线的强度与物质的浓度有抛物线的关系。这个关系式所描述的与在较大浓度范围内一般实验中所观察的一致。

THE RELATION BETWEEN SPECTRAL LINE INTENSITY AND CONCENTRATION OF THE CONSTITUENT IN THE PRESENCE OF SELF-ABSORPTION

The functional relationship between intensity(I) of an emitted line and concentration ( C ) of emitting atoms serves as the physical basis for quantitative spe-ctrochemical analysis. The presence of self-absorption in spectral lines of most laboratory light sources, however, makes the dependence of I on C complicated.A study of variation of slope ( b )of the calibration curve (Si 2516-Fe 2518) with concentration of silicon in cast iron samples by the "transfer method" of spectral analysis was carried out under the condition that within the range of Si content studied, Si 2519 was free from self-absorption and Si 2516, the most intense component of the multiplet was showing self-absorption. A straight line has been obtained by plotting 6 versus log I₂₅₁₉ which was used as a measure of log C. From the slope ( k ) of this straight line, following relationships were derived: b=klogC+β+1,(1) and logI=k/2(logC)²+(β+1)logC+α, (2) where β and α are experimental constants. In the case of Si 2616, the value of k has been found to be about-(1/2) The change of spectral intensity with concentrationin the presence of self-absorption expressed by equation ( 2 ) was found to be in agreement with laboratory observations in general.