A selection of analytical line pairs has been made for use in the spectrographic analysis of low alloy steel. Lines were paired on the basis of similar excitation potentials and wavelength separation. It was found that when excitation potentials of the individual members of a pair were within
${\scriptstyle \frac{2}{3}}$ or
${\scriptstyle \frac{3}{2}}$ of each other, high accuracy and reproducibility were obtained even under conditions of considerable matrix variation, and that within these limits minimum wavelength separation between the lines becomes more important than a closer match in excitation energies for improved reproducibility of line pairs. The lines selected and deviations obtained using these lines under considerable matrix variations are given in tabular form.

Richard N. Kniseley and Velmer A. Fassel J. Opt. Soc. Am. 44(5) 390-393 (1954)

References

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These are the only lines used which do not involve a stable or metastable level. Italicized pairs gave best reproducibility.
These lines are a blend of two lines according to Hurwitz and Convey. However, the MIT Tables list them as spark lines.

Table III

Various source conditions used to test line pairs.^{a}

C(μf)=Capacitance measured at 1000 cycles with a bridge. L(μh)=Inductance calculated from resonant frequency. R(ohms)=dc resistance measured across analytical gap with control gap shorted. Discharges/half cycle=Obtained from 60-cycle oscilloscope trace of condenser voltage. I_{rf}(amperes)=Root mean square current, measured with thermocouple type ammeter. V_{condenser(kilovolts)}=Peak breakdown voltage measured with capacity divider and oscilloscope. I_{Fe}I/I_{Fe}III=Intensity ratio of arc to spark line, FeI3016.185/FeIII3013.12. E_{gap}(watt-sec/discharge)=Energy dissipated in the analytical gap as calculated from E_{gap}=1/n V_{gap}I_{Av}, where n is the number of discharges per second, V_{gap} is the potential drop in volts across the analytical gap (it was assumed to be 50 volts), and I_{Av} is the average current in amperes as calculated from oscilloscope traces of the transient discharge. E_{condenser}(watt-sec/discharge)=Total energy dissipated in a single discharge, calculated from E_{condenser}=CV^{2}/2. J_{0}(amperes)=Peak current calculated from
${J}_{0}=V{(C/L)}^{{\scriptstyle \frac{1}{2}}}$. θ(μ sec)=Duration of discharge determined from oscillograph patterns. f(kc)=Frequency as determined from oscilloscope pattern. N=Number of oscillations per discharge.

These are the only lines used which do not involve a stable or metastable level. Italicized pairs gave best reproducibility.
These lines are a blend of two lines according to Hurwitz and Convey. However, the MIT Tables list them as spark lines.

Table III

Various source conditions used to test line pairs.^{a}

C(μf)=Capacitance measured at 1000 cycles with a bridge. L(μh)=Inductance calculated from resonant frequency. R(ohms)=dc resistance measured across analytical gap with control gap shorted. Discharges/half cycle=Obtained from 60-cycle oscilloscope trace of condenser voltage. I_{rf}(amperes)=Root mean square current, measured with thermocouple type ammeter. V_{condenser(kilovolts)}=Peak breakdown voltage measured with capacity divider and oscilloscope. I_{Fe}I/I_{Fe}III=Intensity ratio of arc to spark line, FeI3016.185/FeIII3013.12. E_{gap}(watt-sec/discharge)=Energy dissipated in the analytical gap as calculated from E_{gap}=1/n V_{gap}I_{Av}, where n is the number of discharges per second, V_{gap} is the potential drop in volts across the analytical gap (it was assumed to be 50 volts), and I_{Av} is the average current in amperes as calculated from oscilloscope traces of the transient discharge. E_{condenser}(watt-sec/discharge)=Total energy dissipated in a single discharge, calculated from E_{condenser}=CV^{2}/2. J_{0}(amperes)=Peak current calculated from
${J}_{0}=V{(C/L)}^{{\scriptstyle \frac{1}{2}}}$. θ(μ sec)=Duration of discharge determined from oscillograph patterns. f(kc)=Frequency as determined from oscilloscope pattern. N=Number of oscillations per discharge.