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5. Dr. Ranjini Raghunandan

Dr. Ranjini Raghunandan

Biography

• 2012-2014:          European Commission 7th Framework Program - Marie Curie Intra European Fellowship.
• 2012-2013:          Swiss National Science Foundation - Prospective Researcher Fellowship. (Declined)
• Designed a Wikipedia webpage for IBBCEAS and ALMA MATER.
• http://en.wikipedia.org/wiki/Incoherent_broad-band_cavity-enhanced_absorption_spectroscopy
• http://laser-spectroscopy.ucc.ie/almamater.html
• Set up of an off axis cavity enhanced diode laser spectrometer with Daniel Tanner, student UCC, as part of undergraduate student summer project 2012.
• Laboratory demonstrations as part of workshop hosted by Physics department, UCC for groups of transition year students.

Research Interests

A very powerful and widely applicable principle to detect trace amounts of gaseous substances is by means of their optical absorption properties. For the detection of halocarbons from seaweed, a cavity-enhanced absorption instrument at the host institute will be developed and advanced - the basic considerations in this context will be outlined in the following. The key qualities of any in situ spectroscopic absorption instrument are its detection sensitivity and species selectivity.

The sensitivity of an absorption method depends on the length over which light can interact with the substance(s) of interest. The sensitivity increases linearly with the absorption path length. Over the past two decades approaches have been developed (mainly for gas detection) that use optically stable cavities consisting of two highly reflecting mirrors (opposing each other) to dramatically increase the absorption path length and hence the sensitivity. Light entering a cavity through one mirror is reflected back and forth many times before leaving the cavity through the other mirror and entering a light detector.

Although many different species may absorb light at one or more wavelengths, the total spectral profile of any particular species is unique - every species has a so-called "spectral fingerprint", which is generally more pronounced in the (near) infrared region than in the visible or UV. The selectivity of an instrument is its ability to distinguish between different species absorbing at similar wavelengths. In practice, selecting an appropriate wavelength range that is specific to a target species can pose a challenge, especially if "interfering" species are present (which will be the case for seaweed emissions). Therefore high spectral resolution methods (such as Fourier transform spectroscopy suggested here) generally have a high selectivity if applied in an appropriate wavelength range.

In this project a cavity-enhanced absorption spectroscopy (CEAS) instrument with improved sensitivity and selectivity for trace gas monitoring will be developed by combining "classical" Fourier transform spectroscopy (FTS) with 'incoherent broadband cavity enhanced absorption spectroscopy' (IBB-CEAS); the latter method was pioneered by the host group.

In addition to FTIBBCEAS, an off axis CEAS spectrometer has been set up to measure biogenic emissions using a more 'conventional' approach using tuneable external cavity diode lasers.  

Publications

• Transform IBBCEAS of DONO and DNO3 between 5500 and 8000 cm-1. R. Raghunandan, A.A. Ruth, J. Orphal. To be subitted to J. Quant. Spect. Rad. Transf.  
• First analysis of the 2v1+3v3 band of NO2 at 7192.1587cm-1. R. Raghunandan, A. Perrin, A.A.Ruth, J. Orphal J. Mol. Spec. 297, 4 (2014).
• Chapter 11 in "Cavity-Enhanced Spectroscopy and Sensing", Eds. H.P.  A. A. Ruth, S. Dixneuf, R. Raghunandan. Lock and G. Gagliardi, Springer Series in Optical Sciences,   Vol 179,2014, XIX, 527.
• Three-level depletion by cavity ringdown absorption spectroscopy. F. J. Mazzotti, L. Barrios, R. Raghunandan, J. P. Maier. Molecular Physics   111, 2 (2013). (Link)
• Renner-Teller and Fermi resonance interactions for the v3 = 1 and v7 = 2 vibronic levels in the A2Πu and X2Πg electronic states of HC4H+. R. Raghunandan, F. J. Mazzotti, A. M. Esmail, J. P. Maier, J. Phys. Chem. A 115, 9365 (2011). (Link)
• Characterization of C4H in the A2Π and X2Σ+ states by double resonance four-wave mixing. F. J. Mazzotti, R. Raghunandan, A. M. Esmail, J. P. Maier, J. J. Chem. Phys. 134, 164303 (2011). (Link)
• Identification of H2CCC as a diffuse interstellar band carrier . P. Maier, G. A. H. Walker, D. A. Bohlender, F. J. Mazzotti, R. Raghunandan, J. Fulara, I. Garkusha, A. Nagy, Astrophys. J. 726, 41 (2011). (Link)
• Electronic spectra of C6H+ and C6H3+ in the gas phase. R. Raghunandan, F. J. Mazzotti, J. P. Maier, J. Am. Soc. Mass Spectrom. 21, 694 (2010). (Link)
• Rotationally resolved ground state vibrational levels of HC2S studied by two-color resonant four-wave mixing. R. Chauhan, F. J. Mazzotti, R. Raghunandan, M. Tulej, J. P. Maier, P. P. Radi, J. Phys. Chem. A 114, 13402 (2009). (Link)
• Selective detection of radicals and ions in a slit-jet discharge by degenerate and two-color four-wave mixing. R. Raghunandan, F. J. Mazzotti, R. Chauhan, M. Tulej, J. P. Maier, J. Phys. Chem. A 113 (4), 13402 (2009). (Link)
• Imaging and interferometric analysis of protein crystal growth. R. Raghunandan, A. S. Gupta, K. Muralidhar, Proc. SPIE6991 69912H (2008) (Link)

Professional Activity

• R. Raghunandan, S. Dixneuf , A. A. Ruth, "Near Infrared Spectroscopy of DONO and Simultaneous Detection of HONO, HNO3 and NO2 by Fourier Transform Incoherent Broadband Cavity-Enhanced Absorption Spectroscopy", Institute of Physics Spring meeting, Dun Laoghaire, Ireland, 2014. (Abstract)
• International meeting on Cavity Enhanced Spectroscopy, Naples, Italy, 2013 ( Link to Poster)
• 7th Conference on Analytical Sciences, Cork, Ireland, 2013.
• Climate change research workshop, Cork, Ireland, 2013.
• F. J. Mazzotti*, R. Raghunandan, A. M. Esmail , L. Barrios, J. P. Maier, "Three-level system depletion spectroscopy by absorption with cavity ringdown", SASP 2012: 18th Symposium on Atomic, Cluster and Surface Physics, Alpe d'Huez, France, Jan 22-27, 2012
• R. Raghunandan*, F. J. Mazzotti, A. M. Esmail and J. P. Maier, "Renner&Teller and Fermi resonance interactions in HC4H+", Frontiers in Spectroscopy: Faraday Discussion 150, Basel, Switzerland, Apr. 6-8, 2011
• R. Raghunandan*, F. J. Mazzotti and J. P. Maier, "Detection of the 3Π - 3Π transition of C6H+ in the gas phase by cavity ring down spectroscopy", POZNAN 2010: The 21st International Conference on High Resolution Molecular Spectroscopy, Poznan, Poland, Sep. 7-11, 2010 .
• F. J. Mazzotti*, R. Raghunandan, A. M. Esmail, M. Tulej and J. P. Maier, "Lowest vibronic energy level characterization of C4H in the close lying X2Σ+ and A2Π states by double resonance four-wave mixing", POZNAN 2010: The 21st International Conference on High Resolution Molecular Spectroscopy, Poznan, Poland, Sep. 7-11, 2010.
• R. Raghunandan*, F. J. Mazzotti, R. Chauhan, M. Tulej and J. P. Maier, "Selective detection of carbon radicals and ions by resonant four-wave mixing spectroscopy", S3C: Symposium on Size Selected Clusters, Brand, Austria, Mar. 8-13, 2009 .
• F. J. Mazotti*, R. Chauhan, R. Raghunandan, M. Tulej, P. P. Radi and J. P. Maier, "Electronic spectra of radicals in a supersonic slit jet discharge by degenerate and two color four-wave mixing", Latsis Symposium: Intramolecular Dynamics, Symmetry and Spectroscopy, Zurich, Switzerland, Sep. 6-10, 2008 .
• R. Chauhan*, F. Mazzotti, R. Raghunandan and J. P. Maier, "Pulsed amplification system of near-IR cw-laser", The Molecular Universe: an International Meeting on the Physics and Chemistry of the Interstellar Medium, Arcachon, France, May 5-8, 2008 .
• R. Raghunandan*, A. S. Gupta and K. Muralidhar, "Imaging and interferometric analysis of protein crystal growth", SPIE Photonics Europe, Strasbourg, France, Apr. 7-10, 2008 .

Teaching Activity

• 2012-2013:          Lecturer of Environmental Physics - University College Cork.
• 2011-2012:          Laboratory Assistant for Physical Chemistry - University of Bern, Switzerland.
• 2008-2011:          Laboratory Assistant for Physical Chemistry - University of Basel, Switzerland.
• Designed a Wikipedia webpage for IBBCEAS and ALMA MATER.
• http://en.wikipedia.org/wiki/Incoherent_broad-band_cavity-enhanced_absorption_spectroscopy
• http://laser-spectroscopy.ucc.ie/almamater.html
• Set up of an off axis cavity enhanced diode laser spectrometer with Daniel Tanner, student UCC, as part of undergraduate student summer project 2012.
• Laboratory demonstrations as part of workshop hosted by Physics department, UCC for groups of transition year students.

Presentations

• Climate change workshop, UCC Ireland (May 29, 2013) Talk
• International Meeting and Summer School on Cavity Enhanced Spectroscopy, Naples, Italy (June 10-13, 2013) Poster
• Conference on Analytical Sciences, UCC Ireland (July 1-2 2013) Poster
• Co-authored book chapter: A. A. Ruth, S. Dixneuf, R. Raghunandan: Broadband cavity-enhanced absorption spectroscopy, chapter 11 of Cavity-enhanced spectroscopy and Sensing. Edited by H.P. Loock and G. Gagliardi for Springer (2013).
  
• R. Raghunandan*, F. J. Mazzotti, J. Fulara, I. Garkusha, A. Nagy, J. P. Maier, G. A. H.Walker and D. A. Bohlender, "C3H2 - A diffuse interstellar band carrier", Molecular Universe - International Astronomical Union 280: Symposium on Astrochemistry, Toledo, Spain, May 30 - Jun. 3, 2011