Final Report Summary - ALMA-MATER (Absorption of light, macro-algae and the atmosphere)
Further experiments in collaboration with the National University of Ireland in Galway were undertaken to study the known emission of I2 from Laminaria Digitata over 6 hour tidal cycles in order to study the ability of the algae to recover from external oxidative stress factors. A separate IBBCEAS spectrometer (working in the visible region of the spectrum) incorporating a flow cell was setup for this purpose and tested. Despite the fact that iodine release from the algae was detected for all samples the dependence on the tidal cycle and the potential of the algae to recover from stress remained inconclusive. Other experiments including the role of H2O2 for the I2 release could also not unequivocally linked to mechanisms that cause the appearance of bursts of iodine release while algae are under oxidative stress. More experiments are planned for the future.
In order to exploit the successful high-end performance of the FT-IBBCEAS setup alternative spectroscopic studies with relevance for atmospheric chemistry were pursued successfully:
1. The near IR spectroscopy of nitrous acid (HONO) and its deuterated counterpart (DONO) and simultaneous detection of HNO3 and NO2 by FT-IBBCEAS was investigated. The relevance of these species is illustrated by a substantial number of spectroscopic studies [7-14]. In ALMA MATER the simultaneous measurement of absorption spectra of these species yielded for the first time information on the 2ν1+ν3 and the 3ν1 bands of the trans-isomers of DONO in the near infrared region between 5500 and 8000 cm-1. All bands were rotationally resolved, and spectroscopic constants could be established with good accuracy. New rotationally resolved bands of DNO3 were also detected. Additionally, several bands of HONO, HNO3 and NO2 have been measured simultaneously across the near IR spectral range, demonstrating the potential of the method to detect multiple trace gases simultaneously through their known line positions (a manuscript in preparation).
2. The very weak 2v1 + 3v3 absorption band of nitrogen dioxide, NO2, located at 7192.159 cm−1 was investigated using Fourier-transform incoherent broadband cavity-enhanced absorption spectroscopy (FT-IBBCEAS) in the 7080–7210 cm−1 spectral range [15]. The energy levels calculation was performed using a theoretical model which explicitly took Coriolis interactions coupling into account as well as spin rotational resonances within the (5, 1, 0), (2, 2,2) and (2, 0, 3) vibrational states. However, the spectral resolution was not sufficient to observe the spin splitting doublets in the spectrum, and the spin-rotation parameters were thus maintained at their ground state values in the theoretical model.
More details can be found at http://laser-spectroscopy.ucc.ie/almamater.html.