6 Minute ReadIntroduction One of the very first posts on this site introduced the basics of Absorption Spectroscopy and the concepts of Absorbance and Transmittance of light through homogeneous materials. In this article we are going to consider this topic in a little more detail through the Beer-Lambert law and use the relationship to determine the concentration […]
The Beer-Lambert Law and Spectrophotometric Analysis Read More »
5 Minute ReadIntroduction Spectrum tubes are a very useful way to introduce science students to the study of the interaction of light photons with matter and the subjext of optical spectroscopy. They are often seen in demonstrations in high schools and early university lab classes to teach the basic principles of quantum theory and atomic and molecular
10 Minute ReadIntroduction This post describes three simple demonstration spectrometers that the home experimenter can set up, with a minimum of optical elements, in order to get involved with examining spectra. These optical design demos are able to capture and record the spectrum of any light source. Whether it is a neon lamp, with its characteristic red
Three Simple “Demo” Spectrometers Read More »
8 Minute ReadIntroduction A thin film can be defined as any material with a thickness ranging from a fraction of a nanometre (nm) to a few microns (μm). The manufacture of thin films onto various substrates is vital to high-tech industries. The deposition of optical coatings, the production of highly integrated chips on silicon wafers, the manufacture
How Thin is a Thin Film? Introduction to Thin Film Reflectometry Read More »
4 Minute ReadIntroduction Many spectral line profiles reported elsewhere on this blog frequently take advantage of a very versatile software package called Spectragryph. The software was developed as a successor to an earlier version for managing and processing spectral data called Spekwin32. Both apps were the creation of Dr. Friedrich Menges who, since 2016, works full time
6 Minute ReadIntroduction Here is the emission spectrum of hydrogen gas in a discharge tube recorded at moderate spectral resolution: Fig. 1 The Spectrum of Hydrogen Gas in a Discharge Tube It was obtained, as with many other emission spectra on this blog, by using either a mini Tesla coil (widely available online) or a high voltage
The Hydrogen (and Deuterium) Emission Spectrum Read More »
9 Minute ReadIntroduction In this post the emission spectra of the Noble Gases are presented. The noble gases constitute the last group (Group 18) in the Periodic Table of the elements. Emission lines obtained from the spectra of these noble gases can be very useful for the calibration of a spectrometer. Historically, these elements were called the
Emission Spectra of the Noble Gases Read More »
3 Minute ReadIntroduction The above image is a sample of high purity caesium chloride crystals (CsCl). They are in a sealed glass ampoule and were prepared under high vacuum. At first glance, these appear to be fairly uninteresting plain white crystals, very typical of so many other inorganic and organic salts. But when these crystals are excited
Caesium Chloride and the F Centre Read More »
6 Minute ReadIntroduction The chemical element Selenium. Atomic number 34. Chemical symbol Se. The quirky title I chose for this post – an element that can’t make up its mind – refers to the fact that selenium is generally considered a nonmetal. However, it has also been classed, by many investigators in the past, as a metalloid.
Selenium: An element that can’t make up its mind Read More »
12 Minute ReadIntroduction The humble Bunsen Burner has been a ubiquitous piece of lab equipment ever since it was invented by the German chemist Robert Bunsen in 1855. A testament to its great success is that this very simple and efficient device still continues to be used in science teaching and research labs all over the world.
The Bunsen Burner, the Swan Bands and the Dicarbon Enigma Read More »
3 Minute ReadIn a previous post I described one of the “workhorses” I have been using for several years for recording spectra. This is the Oriel MS125 spectrometer coupled with an InstaSpec IV CCD (Charge Coupled Device) from Andor Corporation. The main limitation of this system was that the software for the detector only ran under DOS
Freedom from DOS at Last! Read More »
7 Minute ReadIntroduction In a previous post, the phosphorescent properties of several glow-in-the-dark decorative paints were evaluated. The active phosphor in these paints was likely to be europium-doped strontium aluminate. In this post, we examine the emission characteristics of doped strontium aluminate in more detail and record the phosphorescence spectra of these fascinating materials. Some Technical Background
Eu-Doped Strontium Aluminate Phosphorescence Read More »
7 Minute ReadIntroduction There are a number of technical constraints to consider when selecting a spectrometer for a particular application, whether this involves purchasing a commercial model from the wide range of relatviely low cost mini-spectrometers available these days, or whether one is designing and home-building a spectrometer from scratch. In this post we shall consider some
Factors Affecting Spectrometer Performance Read More »
4 Minute ReadIntroduction An off-axis guider is a device well known to all astronomers, professionals and amateurs alike. It usually consists of a compact optical unit inserted between the main imaging camera and the telescope to intercept a small amount of light coming from an astronomical object. Its purpose is to track the motion of that object
Off-Axis Guiders and Sighting Optics Read More »
3 Minute ReadThis is a quick post that examines the spectral line emission changes that occur when a Mercury-Argon (Hg-Ar) gas discharge lamp is switched on and warms up. I used the Time Acquisition mode of an Ocean Optics S2000 fibre-optic spectrometer to record the changes in intensity of 3 spectral lines after the lamp is switched
Mercury Lamp Spectral Changes at Start Up Read More »
3 Minute ReadThe calibration of spectra in wavelength λ that you will see in these different posts has usually been performed with commercial “pencil-type” spectral lamps of mercury-argon Hg(Ar), krypton (Kr) and neon (Ne). These lamps use a continuous AC or DC discharge to excite the inert gases in the tubes and emit a series of narrow
Light Sources for Calibrating Spectrometers Read More »
4 Minute ReadIntroduction Modern spectrometers today, regardless of their size, employ sensitive linear CCD and CMOS sensors. The most popular sizes have 1024, 2048 and more recently 4096 pixels along the dispersion axis of the grating. Associated software automatically reads out a series of digitized values, each value corresponding to a single pixel element on the detector.
Spectrometer Calibration Read More »
13 Minute ReadIntroduction The development of the spectroscope over the last 160 years since its invention has paralleled the evolution in technological advances. This is particularly the case for the last several decades as the development of more efficient electronic detectors have gradually replaced the photographic film. Much progress has been made in this area of detection.
Spectrometer Designs Read More »
4 Minute ReadIntroduction As its name implies, this spectrometer has a fixed diffraction grating. So the wavelength range available and the resolving power (the spectral resolution) are pre-determined during manufacture. Oriel (now Newport Corporation) used to offer 4 models with different wavelength ranges and resolutions for this spectrometer, but I am not sure if these are still
FICS -Fixed Imaging Compact Spectrograph Read More »
3 Minute ReadAbsorbance In very general terms, Absorption Spectroscopy is the spectroscopic technique that considers what happens when electromagnetic radiation of any wavelength passes through a material and some of these wavelengths are absorbed by the substance under study. Very often, visible light is used to analyse the material and the most common substances examined are
Absorption Spectroscopy Read More »
