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