As this isn't directly my area, I'm unable to assist directly. (Perhaps some others who vist this forum occasionally, with background expertise relevant to this area, eg. possibly TakChek?, might be able to help.)
Out of curiosity, what course are you studying and at which level? Eg. are you asking this question more from the academic viewpoint of spectroscopy in general or from the viewpoint of chlorophyll specifically? What exactly are you studying, and where (eg. NUS engineering)?
Finally, depending on what exactly you're looking for (in turn depending on the nature of your course of study), the following excerpt from a biochemistry text might be of some relevance with your query :
http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=stryer&part=A2670