Usage Guide
===========

This guide explains how to use MELT to search and visualize molecular emission lines.

Accessing MELT
--------------

Visit the live tool at https://copland-yz.github.io/MELT/

Works in any modern web browser (Chrome, Firefox, Safari, Edge). No installation required.

Basic Workflow
--------------

1. Filter by Elements
~~~~~~~~~~~~~~~~~~~~~

Click elements in the periodic table:

* **First click** (green) - Include this element
* **Second click** (red) - Exclude this element
* **Third click** (gray) - Reset to neutral

**Example**: You know the system must include C, maybe O and H. You can Click C once (it should look green), then use the |exclude_all| button to quickly exclude all elements at once. Then click O and H once, make them gray. The results will give C\ :sub:`2`\, CO, CH\ :sub:`2`\ O, C\ :sub:`2`\ H\ :sub:`4`\  etc.

.. |exclude_all| image:: exclude_all_button.png
   :alt: Exclude All
   :height: 1.2em 


2. Set Wavelength Range
~~~~~~~~~~~~~~~~~~~~~~~

Enter minimum and maximum values, then select your unit:

* **nm** (nanometers) - Most common
* **Å** (Ångström) - Traditional spectroscopy
* **μm** (micrometers) - Infrared
* **GHz** (gigahertz) - Radio/microwave
* **cm⁻¹** (wavenumber) - IR spectroscopy

**Tip**: Start with small ranges (<100 nm) for faster searches.

3. Search
~~~~~~~~~

Click the "Search" button. Results appear in the table below showing:

* Molecule formula
* Spectroscopic system
* Wavelength (nm and Å)
* Energy levels
* Intensity (when available)
* Source reference

4. Generate Spectrum
~~~~~~~~~~~~~~~~~~~~

To create a synthetic spectrum:

1. Check boxes next to lines you want
2. Set the **Peak Width (FWHM)** to match your instrument resolution
3. Click "Generate Spectrum"
4. Use mouse to zoom/pan the plot

The FWHM (Full Width at Half Maximum) controls peak broadening:

* High resolution: 0.01-0.1 nm
* Medium resolution: 0.1-1 nm
* Low resolution: 1-10 nm

5. Export Data
~~~~~~~~~~~~~~

Download your results:

* **TXT** - Tab-separated text
* **CSV** - For Excel/Sheets
* **PNG** - Spectrum image

Troubleshooting
---------------

No Results Found
~~~~~~~~~~~~~~~~

* Try wider wavelength range
* Remove element filters (reset to gray)
* Check units are correct

Too Many Results
~~~~~~~~~~~~~~~~

* Narrow wavelength range
* Add element filters
* Focus on specific molecules

Spectrum Not Generating
~~~~~~~~~~~~~~~~~~~~~~~~

* Make sure at least one line is selected
* Check FWHM value is reasonable
* Refresh page if needed

Tips
----

* **Small ranges** (<100 nm) search faster
* **Element filters** dramatically speed up searches
* **FWHM** should match your spectrometer resolution
* **Save exports** with descriptive filenames
* **Browser zoom** (Ctrl +/-) adjusts interface size