Direct calculation of long time correlation functions using an optical potential

✍ Scribed by Mercedes Alacid; Claude Leforestier

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 281 KB
• Volume: 68
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1998)68:5<317::aid-qua3>3.0.co;2-y

✦ Synopsis

We present an L L 2 method aimed at directly computing autocorrelation ² < : functions ⌽ ⌽ for systems displaying long time recurrences. By making use of a 0 t w Ž .x Lanczos scheme, as previously proposed by Wyatt Chem. Phys. Lett. 121, 301 1985 , the method avoids explicit time propagation of the wavefunction. The problem associated with spurious recurrences, due to the finite size of the L L 2 -box, is solved in terms of an optical potential located in the asymptotic region. The resulting complex representation of the Hamiltonian operator is handled by a complex symmetric Lanczos scheme, which retains the same basic advantages as its real version. The method is illustrated on the ozone photodissociation process which displays a very detailed recurrence structure over a long time period. It is shown that such a direct calculation of the correlation function is about one order of magnitude faster than an actual wavepacket propagation. The accuracy of the method is assessed by comparison to calculations performed without any optical potential but using a very large box size along the dissociation coordinate.