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 and negative parts Positive and negative parts In mathematics, the positive part of a real or extended real-valued function is defined by the formula Intuitively, the graph of formula_2 is obtained by taking the graph of formula_3, chopping off the part under the "x"-axis, and letting formula_2 take the value zero there. Similarly, the negative part of "f" is defined as Note that both "f" and "f" are non-negative functions. A peculiarity of terminology is that the 'negative part' is neither negative nor a part (like the imaginary part of a complex number is neither imaginary nor a part). The function "f" can