You use 'experimented' when you are trying different things out. e.g. I have experimented with several teaching methods and I have come to the conclusion that... or 'I experimented with drugs when I was younger...' (This is a common use of 'experimented', to say you tried something when you were younger.) You use 'experienced' for something that you felt or well, experienced. e.g. I experienced some changes during my time in the group... 'I have experienced many things during my life...

Use "experience" when you mean to express that you have done or felt something, like "I experienced a nice feeling or a good day at school or that job or talking to foreigners or ... .". but use "experiment" if you want to convey that you are trying to find out something new or you want to discover more about something or ... like "I experimented a new method which was not stated in that recently published paper or ..... "

experienced