Measurement of Small Volume Flame Temperatures by the Two-Line Atomic Fluorescence Method

Abstract

Measurement of small volume temperatures of analytical flames by the two-line atomic fluorescence technique involving the use of direct-line Stokes and anti-Stokes fluorescence of indium and thallium has been examined. Spatial flame temperatures have been measured with a volume resolution of 0.3 mm by 2 mm by 5 mm in the flame. Theoretical and practical considerations of the method are given, particularly in terms of the limitation of using indium or thallium. The use of the two thallium lines (377.57 and 535.05 nm) was subject to fewer random errors than the use of the two indium lines (410.18 and 451.13 nm) for the range of temperatures studied. However, thallium lines are restricted to the measurement of temperatures above about 2000°K (for the air-acetylene and nitrous oxide-acetylene flames); for temperatures below about 2000°K, the fluorescence irradiance ratio could not be measured with sufficient signal/noise ratio due to the low intensity of the anti-Stokes fluorescence line. In the present experiment, indium lines were used for the measurement of a wide range of “low” flame temperatures (approximately 700 to 2600°K) owing to the better signal/noise ratios for both lines; indium lines were also preferable for the air-acetylene flame, even though the error produced by the random uncertainty in the fluorescence ratio was larger than for thallium. The present method has been successfully applied to the measurement of the spatial temperature profiles of analytical flames, such as argon-hydrogen(-entrained air), argon-oxygen-hydrogen, air-acetylene, and nitrous oxide-acetylene.

Diode laser-based thermometry using two-line atomic fluorescence of indium and gallium

“…The main atomic species, so far adopted in TLAF, have been indium [4,6,16,22] with the exception of a few early works which used thallium [12,13]. Thallium was later abandoned due to being temperature insensitive below 3000 K as well as having toxic properties.…”

“…The energy splitting of indium makes it suitable as a temperature marker for flame temperatures above 1000 K [13]. There has, so far, been no investigations into temperature markers for temperatures below 1000 K, which is an important temperature range for low temperature chemistry [23].…”

“…Thirdly, TLAF also has the possibility for thermometry measurements in sooting and particulate-laden flames as the detection wavelength can be shifted from the excitation wavelength [10,11]. The disadvantage of TLAF is that an atomic species, not normally present in the flame, has to be introduced which may add complexities to the experimental set-up.Two-line atomic fluorescence has been developed in steps where the first theoretical ground work was conducted by Alkemade [7] and experimentally demonstrated shortly thereafter using atomic lamps [12,13]. With the advent of suitable lasers, TLAF became a tool for temperature measurements with imaging capabilities in non-steady environments [4,10,11,[14][15][16].…”

“…Two-line atomic fluorescence has been developed in steps where the first theoretical ground work was conducted by Alkemade [7] and experimentally demonstrated shortly thereafter using atomic lamps [12,13]. With the advent of suitable lasers, TLAF became a tool for temperature measurements with imaging capabilities in non-steady environments [4,10,11,[14][15][16].…”

Vapor phase tri-methyl-indium seeding system suitable for high temperature spectroscopy and thermometry

“…Atomic indium is an oft considered tracer, together with atomic thallium, lead, and gallium, for the determination of temperatures in flame when using the two-line atomic fluorescence technique, [1][2][3] as it features spin-orbit components of the atomic ground state that have a significant population at flame temperatures. The most common approach for introducing indium atoms into gas phase uses an indium chloride/water solution, which is either directly aspirated (pneumatic/acoustic) or injected through a capillary into the combustion zone.…”