Atomic and Molecular Spectroscopy Group
The Atomic and Molecular Spectroscopy Group (AMSG) is part of the Space, Plasma and Climate Community of the Department of Physics.
We specialise in high resolution Fourier transform spectrometry (FTS) of atomic and molecular spectra, particularly for astrophysics applications. We have developed unique Fourier transform spectrometers that operate in the ultra-violet (UV) and vacuum ultra-violet (VUV) regions. Our laboratory research also covers spectra from the infrared (IR) and visible regions, and is applied to space plasmas and planetary atmospheric physics. Our current research is funded by the STFC of the UK. We have also been funded by The Royal Society, The Leverhulme Trust, the EU, and PPARC.
Our Research
Our atomic spectroscopy research focuses on the measurement of neutral, singly and doubly ionised transition group and rare-earth element spectra to determine the following parameters;
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Observation of the VUV to IR spectra at high spectral resolving powers (up to a few 106)
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Wavelengths and energy levels (accurate to a few parts in 108)
- Calibrated relative line intensities and oscillator strengths (accurate to a few %)
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Line broadening effects: hyperfine structure and isotope shifts
We have studied spectra of the following elements in recent years: Fe, Mn, Cr, Co, V, Ti, Ni, Mg, Ag, Ta, Mo, Nd and others.
Our measurements are used for fundamental atomic research and theoretical calculations. However, the majority of our research is applied to the study of space plasmas, including;
- Stellar elemental chemical abundances
- Cool stars and brown dwarfs - a stepping stone to extrasolar planets
- Hot stars, red giants, chemically peculiar stars
- Quasar spectra, for the study of possible time variation of the fine structure constant
Further details of our atomic spectroscopy research, and applications of our laboratory data
Molecular spectra are prominent in spectra of cool stars, brown dwarfs, solar system planets and extrasolar planets. High resolution laboratory molecular spectra are needed to help in the analysis of stellar and sub-stellar spectra to determine key atmospheric parameters, including chemical abundances, temperature, dynamics and planetary classification. Our current research focusses on the measurement of:
- Observation of the VUV to IR spectra at high spectral resolving powers (up to a few 106)
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Low/high temperatures, 160K to 500K
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Accurate photoabsorption cross sections
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Wavelengths
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Isotopic shifts
Further details of our molecular spectroscopy research, and applications of our laboratory data
We carry out high resolution experimental spectroscopy with two Fourier transform (FT) spectrometers capable of resolving powers up to a few 106:
- The Imperial College VUV FT spectrometer covering from VUV to the visible
- A Bruker IFS 125HR covering from the visible and to the mid-infrared.
To produce and calibrate spectra, we produce laboratory plasmas with various light sources:
- Hollow cathode lamp
- Penning discharge lamp
- High pressure deuterium lamp
- Tungsten lamp
- Xenon arc lamp
Further details of our instrumentations and related research
The atomic and molecular data we determine become the standard for plasma diagnostics. Thus, we perform lengthy spectral analyses with extreme attention to detail, while innovating techniques as we encounter new challenges. For each species, we carry out:
- Extraction of several 104 spectral lines from spectra with a few 106 data points in length
- Rigorous relative line intensity and wavenumber uncertainty estimations
- Reconstruction of energy level systems from the observed lines
- Improvements to semi-empirical electronic structure calculations
- Many-parameter optimisations to determine nuclear interaction constants from individual lines
- Applications of machine learning algorithms for partial automation
Further details of our analysis and results can be found in our publications and collaborations