Introduction

Combustion is the world’s major source of energy; thus, it is of paramount importance to improve combustion efficiency to effectively use natural resources and minimize combustion-generated pollution to reduce the impact on air quality. Combustion and optical diagnostics have been inter­ twined since Swan’s observation in 1857 of the green bands from C2 emis­ sion in a candle flame. Flames became a good source for optical emission spectroscopy and this early literature is well reviewed in Gaydon’s 1957 book [1].