Dr. Ranjini Raghunandan

Project Title: Absorption of light, macro-algae and the atmosphere (ALMA-MATER).

Link to project page

 

 

Room 118D, Lab 102

Tel:+353-(0)21-490-3294

Tel:+353-(0)21-490-2358

Fax:+353-(0)21-427-6949

Email:r.raghunandan@ucc.ie


 

Research Experience

2012-2014:        Marie Curie Intra European Fellowship, Laser Spectroscopy Group, Physics department, University College Cork, Ireland. Project: Absorption of light, macro-algae and the atmosphere (ALMA-MATER).

2011-2012:        Swiss National Science Foundation Post-doctoral Fellowship. University of Bern, Switzerland. Project: Femtosecond time resolved rotational coherence spectroscopy of non polar molecules.

2007-2011:        Swiss National Science Foundation Doctoral Fellowship, University of Basel, Switzerland. Project: Linear and nonlinear spectroscopic techniques applied to the study of transient molecular species.

2006-2007:        Master's Thesis, Indian Institute of Technology - Kanpur, India. Thesis Title: Imaging and Interferometric Analysis of Protein Crystal Growth.

Teaching Experience

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.

Awards

 

2012-2014:          European Commission 7th Framework Program - Marie Curie Intra European Fellowship.

2012-2013:          Swiss National Science Foundation - Prospective Researcher Fellowship. (Declined)

2011:                  University of Basel - Ph.D. in Physical Chemistry - Summa cum laude.

2007:                  Cochin University of Science and Technology - M.Sc. in Photonics - Gold medal.

2003:                  Cochin University of Science and Technology - Nalanda Endowment Prize for Academic Excellence.

Postdoctoral fellowship

 

Group:              Laser Spectroscopy Group, University College Cork, Ireland.

Supervisor:        Dr. Andy Ruth

Title:                 Absorption of light, macro-algae and the atmosphere (ALMA-MATER)

(Link to project page)

 

Context:

The biogeochemical cycle of iodine is known to have significant impact on atmospheric chemistry, involving intense sea-to-air exchange processes at the marine boundary layers. The role of iodine in polar atmospheres which results in deposition of oxidised mercury in the snowpack, and its oxides leading to formation of aerosol particles in the atmosphere causing ozone depletion has received considerable attention in the recent years. Quantitative data on the magnitude of gas fluxes and the composition of gas mixtures (iodocarbons or molecular iodine) escaping from the sea is essential for models describing aerosol formation and the influence of the corresponding gaseous species on the radiative balance of the Earth and hence on global change. However, data obtained under realistic conditions is sparse due to a lack of technologies that meet the challenges involved in taking meaningful in situ measurements.

 

ALMA-MATER, addresses this problem by Fourier Transform incoherent broadband cavity enhanced absorption spectroscopy (FT-IBBCEAS) in combination with supercontinuum laser sources. Fourier Transform Incoherent Broadband Cavity Enhanced Spectroscopy (FT-IBBCEAS) is a variant of the traditional IBBCEAS setup which uses a Fourier Transform spectrometer for detection of the transmitted light. In this case, the absorption is determined from the Fourier Transform of the intensity of light escaping the cavity. The combination of a Fourier transform spectrometer allows for high spectral resolution to be achievable. The method provides a significant improvement to conventional Fourier Transform spectroscopy for gas applications where small sample volumes are required (e.g. for discharges, combustion plasmas, flames or chemical flow reactors). This approach is being developed in order to identify and characterize biogenic emission sources of iodocarbons in sea water, like the brown macro algae (Laminaria Digitata) which form one of the most efficient iodine accumulators among all living systems. It is planned to study the specimen under controlled stress conditions in the laboratory.

The setup is also being used to study absorptions of gases like HOI, HOBr, HONO etc. which are important to atmospheric chemistry. In addition to the above project, external cavity diode laser based off axis CEAS setup is being setup to be used for detection of iodocarbons and other trace gas species.

Postdoctoral fellowship

 

Group:              University of Bern, Switzerland

Supervisor :       Prof. Dr. Samuel Leutwyler

 

Title:                 Femtosecond time resolved rotational coherence spectroscopy of non-polar molecules.

Context :

Time-resolved femtosecond degenerate four-wave mixing (fs-DFWM) can be applied as a Raman scattering type of rotational coherence spectroscopy (RCS). This background-free rotational Raman technique permits the determination of very accurate rotational and centrifugal distortion constants of the vibrational ground state, and of low-lying thermally populated vibrational levels. Being based on the Raman process, the technique can be applied to investigation of the rotational constants of molecules that do not possess a permanent dipole moment and are not accessible with microwave or millimetre wave spectroscopies.

 

Among the classes of molecules investigated through fs-DFWM include n-alkanes in which the all-trans conformers are inversion symmetric for even n, hence being microwave silent. In the static cell environment, many conformers coexist at room temperature. The technique allows one to study the structural properties of each of the conformers to high accuracy and quantify their abundance. The molecular structures and rotational constants of n-butane through n-heptane in the gas phase have been investigated by electron diffraction measurements on effusive beams at 305-320 K, and both bonded and non-bonded distances have been previously measured. However, the alkane C-C bond lengths are determined to only about ±0.5 pm or about 0.3%. During my postdoctoral stay in Bern, rotational recurrences of n-pentane, n-hexane and n-heptane using fs-DFWM were measured. The other class of molecules studied by the technique is the cyclo-alkanes, and like n-alkanes , these molecules too lack a dipole moment and hence cannot be investigated via the conventional techniques. The cycloalkanes studied during the current project include cyclo-heptane and cyclo-octane.

 

PhD Thesis

Group:               University of Basel, Switzerland

Supervisors:       Prof. Dr. John P. Maier, F.R.S.

Title:                  Electronic spectroscopy of transient molecules by cavity ring down and four-wave mixing.

Context:

Carbon chain radicals and ions have long been known to exist in the interstellar medium, and considered as potential carriers for diffuse interstellar bands (DIBs). Measurements on these molecules are difficult because they are short-lived species generated in small number densities. Discharge and laser vaporization sources coupled to a supersonic jet expansion are, so far, the most effective techniques used to generate sufficiently large densities suitable for spectroscopic studies of these transients. During the studies, these molecular sources were used with high resolution cavity ring down (CRDS) and four wave mixing (FWM) spectroscopic techniques for detection of radicals and ions of astrophysical significance. CRDS offers high sensitivity because of the large absorption path lengths achieved inside the cavity and its immunity towards shot-to-shot laser fluctuations. Four-wave mixing, on the other hand, offers selectivity of the species studied by the application of very short discharge pulse lengths (in the nanosecond time scale), which results in separation of molecule based on their masses, in the plasma discharge.

 

The potential of degenerate and two-color FWM applied to selectivity of transient species was studied extensively using various molecular systems like C3/C4H, C3/HC2S and C2/HC4H+, by varying the timings between the experimental components (laser/valve/discharge) while applying extremely short (<1µs) discharge pulses. The two color variant was shown exceptionally powerful in disentangling overlapping features even within the same spectroscopic system. The first ever detections of ions (HC4H+, C2-) by FWM are also reported in the work. The results suggested convincingly that nonlinear four-wave mixing spectroscopy is applicable to study numerous neutral, cationic and anionic radicals that are produced in plasma environments in low particle densities by applying a discharged free-jet expansion.Both CRDS and FWM were employed as tools for spectroscopic investigation of non-adiabatic effects in linear polyatomic molecules HC4H+ and C4H respectively.

 

CRDS was employed to detect broad absorption features of C6H+ and H2CCC (l-C3H2). The B←X bands of H2CCC match exactly to the profiles and wavelengths of two broad DIBs at at 4881 and 5450 Å, and based on this H2CCC has been identified as a potential DIB carrier.

 

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. SPIE 6991 69912H (2008) (Link)

Conferences

 

Talks

 

 

  • 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

 

Posters

 

 

  • 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 .