Revealing secrets with spectroscopy

This exercise is a part of Educator Guide: Marie Antoinette’s Letters Are Uncensored by X-rays / View Guide

Directions for teachers:

Ask students to read the online Science News article “Ink analysis reveals Marie Antoinette’s letters’ hidden words and who censored them,” and answer the following questions with a partner. A version of the article, “Marie Antoinette’s letters are uncensored by X-rays,” appears in the November 6, 2021 issue of Science News.

In order to answer the first set of questions, students should have a basic understanding of atomic structure and the electromagnetic spectrum. To aid in their brainstorming, you could point students to the Science News for Students article “The ultimate wordfind puzzle.”

Want to make it a virtual lesson? Post the online Science News article to your virtual classroom. Discuss the article and questions with your class on your virtual platform.

Spectroscopy and atomic structure

1. Define and explain the process of spectroscopy based on what you learned from reading the Science News article. What type of electromagnetic radiation did researchers use to study Marie Antoinette’s letters? What data comes out of using the spectroscopic technique?

Spectroscopy is a technique that helps scientists determine the chemical or elemental makeup of a sample. The technique relies on the interaction of electromagnetic radiation (including infrared, ultraviolet, visible, X-rays and gamma rays) with matter. Light is shot from an external source at a sample and based on the sample’s interaction with the light, a spectrum is produced that can help scientists determine what elements or molecules are in the sample. Researchers used X-rays to study the letters’ ink.

2. What happens to the electrons in an atom when certain types of electromagnetic radiation or light interact with it? How does this behavior relate to your understanding of atomic structure?

When electrons in an atom absorb certain types, or wavelengths, of electromagnetic radiation, the particles jump from their stable ground state energy level to a higher energy level. As electrons in atoms jump to higher energy levels, the particles’ most probable locations become farther from the nucleus. When the electrons emit the radiation they absorbed, the particles return to their ground state energy level. This behavior of electrons aligns with electrons existing in discrete energy levels around the nucleus.

3. How did spectroscopy allow scientists to distinguish two separate inks used on the letters? What can you infer about the relationship between elements’ atomic structures and the spectra produced?

The spectrum of each ink was unique because the inks contained different ratios of trace elements such as iron and copper. Each element is made up of atoms that have a unique number of protons, neutrons and electrons. While protons and neutrons reside in atoms’ nuclei, electrons reside in discrete energy levels outside of the nuclei. To jump between energy levels, electrons must absorb and emit radiation at energies that are specific to each element. As a result, scientists can ID elements in a sample based on the radiation energy that the sample absorbs and/or emits.        

4. Draw a simple diagram of the process of X-ray fluorescence spectroscopy. Make sure you show the external light source, the ink and the result of the interaction. In another diagram, draw the light’s interaction with an electron in one of the atoms in the ink. 

Student answers will vary, but should include X-ray light shining on the ink and the ink absorbing the light and then emitting light. Students may show that a detector will display a spectrum from the sample. In their diagram of the atom, students should show light being absorbed when an electron moves from a ground energy level to an excited energy level, and light being emitted from the reverse process.

More mysteries to solve

1. Brainstorm examples of other historical or scientific mysteries that could be solved using spectroscopy.

Student answers will vary, but could focus on historical artifacts such as art and documents, or scientific artifacts such as fossils. Examples of mysteries could be authenticating the artifacts, knowing where they came from and who created them.

2. Beyond the information gathered using spectroscopy, what else would you need to know to solve one of the mysteries that you brainstormed?

Students should focus on the need for context to make sense of any discoveries. Scientists can gather data about an artifact, but to truly solve a mystery, they would need to combine that with historical or scientific context from the artifact’s time period.

3. Discuss what ethical issues exist around uncovering messages that were purposely concealed. What other ethical concerns should researchers consider when solving historical mysteries? What ethical concerns might you need to consider when solving one of the mysteries that you brainstormed?

Students should discuss whether or not it is ethical to have scientists uncover redacted material and share it with the public.