How do you understand a definition of the constant breakdown?

The breakdown constant Cbd includes the information about the dielectric strength

of the gas that depends on the gas composition. Different gases have different mean free paths for molecules and electrons affecting the breakdown voltage and the energy released by the spark breakdown among the gas column between the electrodes.

Please check this work - http://digitalcommons.mtu.edu/cgi/viewcontent.cgi?article=1424&context=etds

Thank you very much sir.

But i want to know the behaviour of ethanol-gasoline just after the glow discharge phase of spark plug. As every gas (total charge inside the cylinder) acts as insulator so it requires certain breakdown energy(Activation energy included). for that calculation i require breakdown constant.