Documentation for the Atomic Emissions package

Fri Jul 25 18:56:07 PDT 1997

Abstract

The Atomic Emissions applet demonstrates the behavior of an electron as it changes states in the orbit of an atom, by absorbing energy and emitting photons.
This document gives an overview of use and a history of the creation of this applet.
All sourcecode to the classes contained in this package, except those specified below, are Copyright (C) 1997 by the University of Oregon


Documentation for the Atomic Emissions package

Table of Contents

1. Mechanics
    1.1 Equations
    1.2 Units
    1.3 Constants
    1.4 Accuracy
    1.5 Applet components
    1.6 Measured items
2. Credits
    2.1 Concept
    2.2 Graphics
    2.3 Programming
    2.4 The Virtual Laboratory

1. Mechanics

1.1 Equations

Values are computed with the following equations:

wavelength (l)
l = hc/e
energy (e)
e = hc/l

1.2 Units

wavelengths (l)
Angstroms
energy (e)
electron volts

1.3 Constants

Plank's constant (h)
2 * PI * 0.6582E-15
The speed of light (c)
299792458

1.4 Accuracy

All of the calculations are precise to 16 bits. Some calculations are done in 32 bits, but are then rounded to 16 bits. Wavelengths are displayed as integers (the floating point part is truncated, not rounded). At times, wavelengths are considered equal if they are equal to two decimal places. PI is a 32 bit floating point number.

1.5 Applet components

There are three distinct applets which can be used in varying combinations.

AtomicEmission
The main applet. This applet shows the electron states and an electron, and displays the waves which are emitted from state changes. This applet can be set up to be either a passive receptor for light, for use with the LightSource applet, or as an interactive applet where the user chooses the state changes. The interactive function of the applet allows the user to choose a state to which the electron is excited. They then may choose the first state the electron drops to. After this, the electron drops to states chosen at random until the electron is at the ground state. The energy states have energy levels defined in an applet parameter tag, as are the probabilities that the electron will drop to any given state below.
LightSource
The LightSource applet is attached to an instance of the AtomicEmission applet (specified by a name attribute in the applet tag of the AtomicEmission applet). It allows the user to choose from a set of wavelengths should this be energy levels? and then start the emission of photons. Photons strike the AtomicEmission atom, which absorbs the energy, and begins a state change process.
SpectralOutput
This applet provides a graph of the number of photons of each wavelength which have been emitted by a given instance of the AtomicEmission applet (attached as is the LightSource applet)

Two of the applets, SpectralOutput and LightSource, are useless if not attached to an AtomicEmission applet. SpectralOutput may be used without LightSource being used, but it makes little sense to use LightSource without using SpectralOutput.

Behavior of the AtomicEmission applet (which in some cases effects the behavior of the other applets) can be modified:

  1. The delay between state changes can be specified by a parameter applet tag to the AtomicEmission applet. It makes sense to lower this value for automatic generation of largish amounts of data. This parameter's name is delay, and values are specified in milliseconds. This parameter defaults to 1500.
  2. The interactivity of the AtomicEmission applet is also toggled by a parameter tag. The parameter's name is interactive and the value is either true or false. This parameter defaults to a value of true.
  3. A third tag specifies the starting state of the electron. This is for simulation of atoms in high-energy environments, such as suns, where the collisions of atoms keeps the electrons in a constantly excited state. This parameter is named start state and is given an energy level for a value. The default value is the ground, or lowest, state.

1.6 Measured items

Wavelengths, energy levels, and frequency statistics are reported by the AtomicEmissions and SpectralOutput applets.

2. Credits

2.1 Concept

The idea for this applet was presented by Greg Bothun. Dr. Bothun is a professor of astrophysics at the University of Oregon and one of the most prolific faculty members of this campus.

2.2 Graphics

Most, if not all, of the non-trivial graphics are provided by Amy Hulse, a graphic artist under the employ of Dr. Bothun. All other graphics, IE, the ugly stuff, is Sean's fault. The AtomicEmissions applet unfortunately does not contain any of Amy's work.

2.3 Programming

All applets at this site have been programmed by Sean Russell. Sean is a full time software developer in the employ of Dr. Bothun. The AtomicEmissions applet uses two third-party packages:
  1. The XML parser is Lark, a really nifty XML parser that I discovered after completing about 50% of an XML parser of my own. Funny thing is, the documentation for Lark contains no mention of who the author is or how to contact him, but if you poke around on Textuality's site, you will find out that Textuality is the consulting firm of Tim Bray. Thanks, Tim!
  2. The graph tool is part of the teaset java package, which is a simply huge package of pretty useful classes. The home page for the people who develop the Tea Set is the InetSoft page.

2.4 The Virtual Laboratory

The Virtual Laboratory is a research project that endeavors to discover if the quality and availability of education can be improved by changing the course material to online, interactive multi-media. We strive:
  1. To improve general access to higher education resources
  2. To stimulate the desire to learn
  3. To provide a simulated increase in university resourses
  4. To increase up-to-date, dynamic information access for students.

This document was generated from the XML by Lark's xh processor.