Category: Spectroscopy

Posted in Spectroscopy

How to Discern Education vs. Propaganda

Posted on by D. L. Williams

Ken is one of my favorite thinkers and bloggers. I hope you enjoy his latest post:

Reflections

There is a lot of discussion these days about things like fake news, yellow journalism, and political propaganda. There is also a lot of attention given to whether public schools and colleges in our time educate or indoctrinate when it comes to the instruction of their students. So what’s the difference between education and propaganda? Let’s look at seven ways education differs from propaganda.

First, we’ll define three key terms:

Education is the pursuit and discovery of information, knowledge, truth, and wisdom through critical analysis. That process of discovery can be unaided (self-study) or aided (teachers). The goal of education is for the student to develop the ability to form an independent, reasonable judgment of the topics studied.

Indoctrination can mean mere instruction in a given topic, but it often carries the pejorative meaning of inculcating ideas in an uncritical manner. This approach to teaching can be well-intentioned but, from an educational standpoint, it is…

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Posted in Education, Physical Chemistry, Science Education, Spectroscopy, UV-VIS-NIR, working problems

Spectrum of a Particle in a 1D Box

Posted on by D. L. Williams

It is safe to say that every physical chemistry course teaches the Particle in a Box problem as an introduction to quantum mechanics. I have taught it also in my course for years.

I have been bothered for years, however, by the fact that the text books stop after solving the Schrodinger equation. All of them that we have surveyed do this. McQuarrie, Atkins, Engel, Levine, etc.

This is a shame because we can’t detect the energy levels by themselves. Quantum theory was invented to explain spectroscopy. So why not take the 1D Particle in a Box (1DPB) problem all the way to a simulated spectrum?

At SHSU, we do.

Here are three lectures that explain what I do with the Particle in a Box.

(Be patient with the Kahoot quizzes and end of class Q&A. Feel free to skip ahead, or try to answer the questions in your own mind to see how you do! To find all my Kahoot content search for my username chem_prof on Kahoot. I have Quantum, Thermo, and Forensic Chem Kahoots.)

Lecture 1 – Managing the Messy Mathematics

This lecture takes the spectrum of a 1DPB apart to show what pieces of the spectrum are explained by quantum theory.

TN-L3

Lecture 2 – The Schrodinger Equation

This lecture is the traditional presentation of the 1DPB problem – normalizing the wave functions and solving for the energies via the Schrodinger equation.

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Lecture 3 – Spectral Transitions and Spectral Assignments

This lecture discusses spectral transitions, the transition moment integrals and the transition equation which tells us about the spacing of our spectral lines. The transition equation also tells us about the quantum system if we begin with an experimental spectrum and assign the quantum transitions.

clip-spectral-assignment

What are your reactions to this approach? I’d love to hear from you in the comments section. I am preparing this material for a book for students to read in the summer prior to taking pchem. I think it will greatly help to get them thinking about our quantum world early and often.

Happy Pchemming!

Darren Williams

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

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.