VIBRATIONAL STATES OF CARBON DIOXIDE AND OTHER GREENHOUSE GASES Bonding occurs when atomic orbitals of adjacent atoms overlap (pz and pz). The result is a space in which electrons are shared between the two atoms (pink area in the boxed image). Vibrational Energy States of Carbon Dioxide (CO2) The bond length (distance between bonded nuclei) is not rigid and constant-- it is dynamic and varies in size continuously in response to its environmental conditions (temperature, radiation, pressure, etc). Symmetric Antisymmetric In-plane What happens when light interacts with matter? stretching stretching scissoring (See the 1-pager for reference) If there's a match between the wavelength of incoming radiation and the bond length of the molecule it strikes, then the molecule absorbs the energy of the incoming In-plane Out-of-plane Out-of-plane photons and vibrates. Restating that in a more rocking wagging twisting technical way, the excited molecule occupies a variety of vibrational states. EXAMPLE: When CO2 absorbs infrared (IR) radiation: The energy of IR wavelengths matches the length of carbon-oxygen bond. Like a guitar string, the bond length resonates with the wavelength of the incoming IR radiation. The energy (hf) of that radiation pushes the molecule into every possible vibrational energy state available. Animated interactives make it easier to see these for three greenhouse gases, H2Q, CO2 (carbon dioxide) and CHA (methane). Play with each of the three molecules to see their various vibrational states, then answer the questions below. Vibrations of Carbon Dioxide Vibrations of Water CONTROLS CONTROLS orresponding to the movements using the check boxes to optimise the view. Advanced - The symmetry for each vibration is also shown. Show all vibrations vibration vectors Click here & see all vibe modes animated together color vectors yellow O color vectors purple spacefill off O spacefill 20% ( spacefill 100%% 3N-5 frequencies for linear systems of N atoms 3N-6 frequencies for non-linear systems of N atoms Other molecules to explore Hydrogen Cyanide | Carbon Dioxide | Water | Ammonia | Boron Trifluoride | Methane | Ethylene(Ethene) | PF | Fe(CO) | Benzene Click here to see individual vibe mode 73 JSmol JSmol * *#*# 4 (2) 641.49 cm Plu 1711.15 cm1 41 How useful was this page? Answer these Questions: 1. It is often said that CH, is a "more powerful" greenhouse gas than CO2. Ignoring all other factors about these two atmospheric gases and comparing only the vibrational states of methane with those of carbon dioxide, explain what would make this claim plausible. 2. There is more to the greenhouse effect than just the bond lengths of molecules and the frequency of incoming and outgoing radiation. List any other factors that could be operative here