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 Affect Schedule valid instrument in the assessment of positive and negative affect. The PANAS was developed in 1988 by researchers from the University of Minnesota and Southern Methodist University. Previous mood measures have shown correlations of variable strength between positive and negative affect, and these same measures have questionable reliability and validity. Watson, Clark, and Tellegen developed the PANAS in an attempt to provide a better, purer measure of each of these dimensions. The researchers extracted 60 terms from the factor analyses of Michael Zevon and Tellegen shown to be relatively accurate markers of either positive or negative affect, but not both.