high resolution mass spectrometry

• what is low resolution mass spectrometry used for?

  to measure Ar to 1dp
• what does it mean if 1 peak is produced with low resolution mass spectrometry?

  same Mr

  different molecular formula
• what is high resolution mass spectrometry used for?

  to measure Ar to 4dp
• what does it mean if 2 peaks are produced with high resolution mass spectrometry?

  same Mr

  different molecular formula
• why does high resolution mass spectrometry not separate isomers?

  exact same molecular formula so same Mr to 4dp
• what is a radical cation?

  species formed when compound is struck by fast moving electrons