Category: Spectroscopy

Posted in Contact Angle, Critical Solution Temperature, D L Williams, DSC, Education, Forensics, FTIR, Hansen Solubility Parameters, LIF, Physical Chemistry, Raman, RER, Science Education, Solubility, Solvent Blending, Spectroscopy, Thermal Analysis, UV-VIS-NIR, XPS

PCHEM and Forensic Chem Lecture Videos

Posted on by D. L. Williams

I frequently have seniors who want to revisit the concepts in pchem sit in my 8AM lectures the year after they have had my course. It’s a privilege to have them and an encouragement to see their natural curiosity in action. They seek to firm up their understanding of the quantum world and how we interact with it (i.e. spectroscopy).

In the fall of 2017, I put these students to work videoing the lectures and posting them on the Physical Chemistry at Sam Channel. These videos are essentially raw footage of lecture. The videos could have been greatly improved by adding in the PowerPoint Slides, captioning, cleaning up the audio, and cutting out my “ums” and “uhs”. But these volunteers did not have time to do that, nor did I. I had a CLEANING WORKSHOP to plan and execute!

CHEM 4448 – Physical Chemistry 1
– Quantum Mechanics and Spectroscopy

CHEM4448-Playlist-Snip

CHEM 4449 – Physical Chemistry 2 -Thermodynamics

4449Lecture-Playlist-Snip

CHEM 4380 – Forensic Chemistry

The students appreciated the fall lecture videos so much, there was a great amount of interest in capturing the Forensic Chemistry Lectures. So we created a Forensic Chemistry at Sam Channel, too.

CHEM4380-Playlist-Snip

The lecture playlist is only one piece. Jessy also created other playlists of videos on the Forensic Chemistry at Sam Channel that should interest Forensic Science and Forensic Chemistry students and enthusiasts. She performed these tasks as an SHSU Honors Contract for the course – an activity that supplements the material for the student and enhances the skills that they take away from the course.

Thanks to the Student Team!

Even raw footage must be stitched together, uploaded, described, tagged, and set up on YouTube. This takes TIME and time is a valuable commodity for our chemistry majors.

I thank William Fernandez for videoing CHEM 4448 and CHEM 4449. His videos were so well-received by the students that Jerome Butler decided to sit in and video my Forensic Chemistry course CHEM 4380. Thanks Jerome!

I thank Matthew Peavy for producing the videos for CHEM 4448 and CHEM 4449, and for uploading them. I thank Jessy Stone for producing and uploading the CHEM 4380 videos for Forensic Chemistry.

You students who are willing to go beyond the minimum give us hope for the future.

You people in industry and in graduate programs, hire these students! You won’t be sorry!

-DW

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Posted in Education, Philosophy, Physical Chemistry, Spectroscopy

Why Do I Love Pchem?

Posted on by D. L. Williams

abstract-concrete

Pchem, how do I love thee?
Let me count the ways…

1. Pchem connects abstract concepts to concrete reality.

The concept of the wave nature of light and matter is very abstract. It is not directly measurable. But the mathematics of interacting waves allows us to predict the interactions of light and matter. This is called spectroscopy.

Your eyes are pigment-based spectrometers detecting light at different wavelengths giving you the ability to perceive what we call color.

From these abstract wave equations we get concrete products like laser pointers and digital cameras. And I love it!

2. Pchem simulates natural phenomena well.

Some of the spectroscopic simulations I have seen in pchem have been truly amazing. To appreciate this, one may need a micro-course in statistics.

The R² value can be thought of as “how much scatter in the data is explained by your model”.

A decent calibration curve in an environmental lab or water quality lab will have a 99.95% R² value, meaning that the calibration model captures 99.95% of the scatter in the data.

The R² value for modeling the rotational-vibrational spectroscopic transitions in carbon monoxide is often 99.9996% or better. This means our pchem model for molecular vibration and rotation is capable of capturing over 99.999% of the variation in the data.  That’s crazy-good! In fact, this model is so detailed, we can tell how much the CO bond length stretches as it spins faster and faster. I love that!

3. Pchem transforms your imagination.

OK. So the wave function concept allows us to simulate nature and to produce exciting gadgets. But what IS the wave function, ontologically?

This is perhaps the most exciting thing about pchem. It transforms your imagination. I am drawn to think deeply about the wave nature of matter, the balance of Coulombic attraction and repulsion, the coupling of intrinsic angular momentum.

What IS the angular momentum of a WAVE?

Where IS the mass in a WAVE?

What (or WHO) sustains these never-decaying ground state wave functions?

Amazing questions for an amazing life of the mind, which is another reason I love pchem.

Posted in Spectroscopy

Excel Roller Coaster – Yes, my hobby is Excel

Posted on by D. L. Williams

If you have FUN programming Excel, on a SATURDAY…You MIGHT be a Redneck I mean, you might be a PCHEMIST.

DLWilliamsExcelRollerCoaster1

Years ago, I was at home on a Saturday fiddling with a wave function problem in Excel. The plot on the screen was of a couple of cosines, and my 8-year-old son said, “Hey that looks like a roller coaster”.

“It sure does.” I said. “Do you want to make a roller coaster in Excel?”

“Yes!”, he said.

So over the next four hours we had some quality father son time making a roller coaster in Excel. He learned something about cosine functions, and how to put custom backgrounds on a chart. Some of the finer details he did not care much for were anchoring cells, negative error bars, or the mod() function. But he really appreciated the custom look of a white wooden roller coaster and the looping macro that made the coaster run along the track.

You can download the macro-enabled (.xlsm) workbook file from my curiosities page to see how these functions and settings were used. Here is a time-lapse video of my creating the page from scratch. There are some fun tricks so I hope you enjoy it. the background loop is a bit annoying. Sorry.

The coaster uses an infinite loop. To kill it just click Ctrl+Break, and it will stop.

What Excel awesomeness to you have to share? What questions do you have about these functions and settings in this fun application?

Ask in the comments field, and subscribe for more fun in the future (like my Sudoku solving spreadsheet).

Posted in Spectroscopy

Fall Cleaning

Posted on by D. L. Williams

Forget Spring. I just purchased a lot of optics, and before I rip them from their protective packaging, I had better review my handling and cleaning techniques.

cleaningsupplies

Fortunately for me, Edmund Optics – the company that sold said optics – is savvy enough to send an email approximately 2 weeks after my purchase with guidelines and reminders about how to care for my optics. Here is their first paragraph followed by a link to the rest of their article. (This is not a sole endorsement of EO, but it is an acknowledgement that this 2-week email practice rocks.)

From EO:

“After purchasing an optical component, exercising proper care can maintain its quality and extend its usable lifetime. Choosing the proper cleaning products and using the proper methods are as important as cleaning the component itself. Improper cleaning practices can damage polished surfaces or specialized coatings that have been used on optics such as lenses, mirrors, filters, or gratings, degrading the performance in almost any application. Also, be aware of your clothing and your environment while cleaning optics; shirts with zippers and buttons can scratch your optics, likewise dirty or dusty environments are not well suited for optical applications.”

Continue reading…

Enjoy!

:DW

Posted in Spectroscopy

PChem at SHSU, What to Expect

Posted on by D. L. Williams

Most of our frustration in life stems from incorrect expectations. So let me line out the year of PChem at SHSU so you will not be frustrated by the unknown.

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Starting at 30,000 ft elevation, we have the two semesters:
Fall is Quantum Mechanics and Spectroscopy
Spring is Thermodynamics

Zooming in on the Fall semester, we have the following structure.
Quantum Mechanics, Spectroscopy, and Group Theory fully developed on one-dimensional systems.
QM applied to vibrational spectra
QM applied to rovibrational spectra
QM applied to atomic spectra
QM applied to electronic molecular spectra
Spectral simulation with Gaussian

This is a significant departure from the structure of my undergraduate pchem course at UT in the late 80’s. And in my opinion, it is a great improvement!

My goal for the class is for the students to be able to apply a quantum view of light interacting with matter whenever necessary.

I know this approach has been successful because alumni have written me saying that they were able to understand spectroscopic applications not covered in my course. This course gave them the skills to apply the theory in new situations, which is the greatest goal of higher education.

Drilling down into Thermodynamics, I break the course into five sections.
Statistical Thermo taking quantum theory to bulk properties.
Thermochemistry the theory of bulk properties and engines.
Phase diagrams, pure substances, mixtures, and equilibrium.
Non-equilibrium systems and transport phenomena.
Energy sources, sinks, conversion, and efficiency.

This is also a departure from the traditional pchem Thermo treatment, which in my experience was a class in partial differential equations taught under the guise of a chemistry class.

Is this treatment effective? Once again, I rely on alumni to support my claim that it is. They are well employed and advancing in GE, Baker Hughes, Nalco, Agilent, and other competitive companies.

Posted in Education, Physical Chemistry, Science Education, Spectroscopy

What is pchem?

Posted on by D. L. Williams
Pchem is short for Physical Chemistry. It is hated by all. It is SO bad (the audience asks, “How bad is it?”), that it has it’s own bumper sticker!
p-chem
Why is pchem so mistreated?
Like a scientific tax accountant, a P-chemist worries about the energetic balance sheet, the gains and losses of energy, the ratio of usable to unusable energy. We pull the thread through all states of matter – liquid, solid, gas, plasma, elastic, plastic, glass, etc.
My favorite subsection of pchem is symmetry and spectroscopy. Spectroscopy is the study of light interacting with matter. And symmetry is used to decipher these interactions. There is no better example of the mathematical beauty of our universe than the unexpected explanatory power of group theory as it applies to absorption and emission of light.
Fireworks, hair dye, crayons, ink, glow sticks, lightning bugs, and all the rest can be understood through pchem – specifically my field of spectroscopy.
There is much more to pchem. If you have made it this far, then you are truly curious. Therefore, I give you the table of contents to a typical pchem textbook. (You will have to “Look Inside” at the Amazon site to view the TOC.)
And, I ask you to share and subscribe to this blog. Comment below with suggestions for posts.
Posted in Education, Spectroscopy, UV-VIS-NIR

What makes a rainbow?

Posted on by D. L. Williams

All of us love a rainbow, and a double rainbow is even more exciting. This is pchem* in action!

350px-Double-Rainbow
A double rainbow photographed in Karlsruhe on July 22, 2011. Leonardo Weiss http://commons.wikimedia.org/wiki/File:Double-Rainbow.jpg

You may have noticed that rainbows only appear with the sun at your back. Why?

Rainbows are angle-dependent. The light coming from behind you hits water drops of a particular size and at a particular angle so that they are diffracted (bent) inside the drop. This can occur in a clockwise or counter clockwise manner. The clockwise path through the drop to your eye and the counter-clockwise path occur at slightly different angles. This creates the two rainbows.

The different wavelengths of light from red to blue also travel at slightly different angles (just like through a prism), and this creates the spread of colors in each rainbow.

Have you ever seen a triple or higher-numbered set of rainbows?

Some will brag and say they have. But this is extremely improbable. If their eyes were sensitive enough to see this higher-order diffraction, then they would be blinded by the bright sunlight needed to produce the rainbow in the first place. The probability of light traveling multiple circles within the water drops to create second- (and higher-) order diffraction effects is very slim compared to the single pass rainbows that we are all familiar with.

Post links to your favorite rainbow images in the comment section.

Subscribe to this blog for more Pchem* topics.

*Pchem (Physical Chemistry) is the study of the physical properties of the universe.