Mr.Rajiv Kumar, Let me to give a different opinion.
Eventhough you have not mentioned the name of the Act, under which you are seeking the information, the PIO cannot reject your application under the ground non mentioning of the name of the Act. Because you have addressed as " The Public Information Officer ".
The PIO is an authority appointed under RTI Act, 2005.
So I hope that the application addressed to the PIO automatically amounts that your application is under RTI Act, 2005.
If information furnished above found to be incorrect by any expert please excuse me.