Orbitals may be visualized using several different options, including slices along the xy, yz, or xz planes and first quadrant-only sections. Colors can be selected to emphasize probability or the sign of the wavefunction. Any orbital up through principal quantum number n = 20 for nuclear charge Z up to 120 may be displayed and may involve from 625 to 320,000 points. As the orbital is produced, the progress of the Monte Carlo calculation can be monitored in the form of a developing histogram of number of “hits” versus radius. This histogram can be compared to a plot of theoretical radial probability either in three-dimensional space or in the selected planes. Quantum numbers n, l, and m may be selected either by direct entry or by pointing to orbitals on an energy level diagram. In addition, the hydrogen atom emission spectrum can be displayed. The correlation between lines on the emission spectrum and transitions between energy states can be easily correlated.

Accompanying the program is an HTML help file that discusses the Monte Carlo method, presents program options, and provides the context in which the program is used at St. Olaf College (a second-semester laboratory experiment relating to atomic spectroscopy).

A screen from ORBITAL.

ORBITAL requires the following software, which is available for free download from the Internet: Netscape Navigator, version 4.75 or higher, or Microsoft Internet Explorer, version 5.0 or higher; Chime Plug-in, version compatible with your OS and browser (available from MDL).