A theoretical study of the high-order harmonics of a 200 nm laser from H<SUB>2</SUB> and HeH<SUP>+</SUP>

Using a time-dependent quantum mechanical method, based on the evolution of the electron density in real time, a theoretical study is made of the high harmonic generation in H<SUB>2</SUB> and HeH<SUP>+</SUP>, corresponding to a 200 nm laser. For H<SUB>2</SUB>, four laser intensities in the range 10<SUP>13</SUP>-10<SUP>16</SUP> W cm<SUP>-2</SUP> are employed while only one intensity ( &#8776; 10<SUP>16</SUP> W cm<SUP>-2</SUP>) is employed for HeH<SUP>+</SUP>. Up to the 45th order (4.44 nm) harmonic for H<SUB>2</SUB> and the 53rd order (3.77 nm) harmonic in HeH<SUP>+</SUP> are predicted. For H<SUB>2</SUB>, increase in laser intensity I does not change the structure of the high harmonic spectrum but increases the yield of each harmonic according to a fractional law of I<SUP>1.5</SUP>. Polar molecules/molecular ions might serve as excellent sources for higher harmonics, the yield and order of the harmonic increasing with increasing mass, ionization potential and polarizability