Introduction

Abstract

In practice, a scientist who investigates atomic and molecular systems may face a situation when information about parameters of atoms and molecules is required. Then, one must turn to the relevant reference material, reviews, or original papers. It is good if one knows where to find these parameters and has an idea of reliability in determining the data involved. However, it may just as well be that the information required goes beyond the sphere of one’s own scientific interests. In this case, the values of quantities to be determined are of primary significance, provided they are reliable, and how this information was obtained is of little importance or, sometimes, “interest”. As is proved by experience, the aid of an expert is necessary to give guidelines in the search for such information and especially in an estimation of its reliability. Thus, offering the reader a “Reference Data on Atoms, Molecules and Ions” we presume to be such experts who have selected the most useful data on the parameters of atomic and molecular species, the error estimation of the data involved being given throughout.