Dear Surya.
Before answer your question more experimental detail needed. What power of your exitation? Could you attach Raman spectra from both exitation?
Sir
I have tried with various powers ranging from 10 % to .05% of Ar ion laser. But couldn't get any spectra. Through literature I came to know that in order to obtain Raman spectra of Hafnia people are using Nd YAG laser of wavelenght 532 nm. I am confused that Ar ion as well as Nd YAG are very much close in energy but still how Nd YAG gives a a wide range of bands and Ar ion laser doesn't even give one peak.
Dear Surya,
Indeed, it is really strange than your instrument didn't show any line with excitation at 514 nm. But it possible due to many reasons. You should check that you use equal power on sample (in mW) not in percentage of maximum of you laser power. Check that you could acquire Raman spectra from some different test sample from both source (may be you have a bad laser entrance alignment). Next step try to increase accumulation time at 514 by several time.
Kind regards,
Alexander
Dear Surya,
Not knowing the details of your experiment, I envision two possible reasons. In decreasing order of probability :
- The peak power of your YAG laser is much larger than the mean value of your argon laser so that you might be observing hyper-Raman with the former but not with the later. Decreasing the peak power of the YAG pulses should kill the Raman line intensity according to a power law.
- There might be a narrow electronic state in your material close to the 532 nm line that could resonantly enhance the Raman lines for the YAG not for the argon laser. An absorption or excitation spectrum should be enough to solve your puzzle. You could also vary the temperature of your sample in order to move away this hypothetical line from the 532 nm line.
Thank You Prof. Charles Hirlimann. I will try taking temperature dependent measurements.
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