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 excess has been reciprocated. For formula_15 the sequence terminates with an exact fractional expression of formula_16, and for quadratic irrational formula_16 the sequence becomes a periodic continued fraction. In the study of classical groups, for every formula_18, the determinant gives a map from matrices over the reals to the real numbers formula_19 Restricting to invertible matrices gives a map from the general linear group to non-zero real numbers: formula_20. Restricting to matrices with a positive determinant gives the map formula_21; interpreting the image as a quotient group by the normal subgroup relation expresses the positive reals as a Lie group.