Chemical ionization source, the reagent gas is present in large excess compared to the analyte. Electrons entering the source with energy around 200-500 eV will preferentially ionize the reagent gas. Then, the ion/molecule reactions produces more stable reagent ions and the resultant collisions with other reagent gas molecules will create an ionization plasma. Positive and negative ions of the analyte are formed by reactions with this plasma. The following reactions are possible with methane as the reagent gas. If ammonia is the reagent gas, For isobutane as the reagent gas, Self chemical ionization is possible if the reagent ion is an ionized
Positive real numbers of the logarithmic scale. For purposes of international standards ISO 80000-3 the dimensionless quantities are referred to as levels. Positive real numbers In mathematics, the set of positive real numbers, formula_1, is the subset of those real numbers that are greater than zero. The non-negative real numbers, formula_2, also include zero. The symbols formula_3 and formula_4 are ambiguously used for either of these, so it safer to always specify which. In a complex plane, formula_5 is identified with the positive real axis and is usually drawn as a horizontal ray. This ray is used as reference in the polar form