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
Negative base For example, the numbers from 100 to 109 have the same representations in decimal and negadecimal. Similarly, and is represented by 10001 in binary and 10001 in negabinary. Some numbers with their expansions in a number of positive and corresponding negative bases are: Note that the base expansions of negative integers have an even number of digits, while the base expansions of the non-negative integers have an odd number of digits. The base expansion of a number can be found by repeated division by , recording the non-negative remainders of formula_3, and concatenating those remainders, starting with the last. Note