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Manuscript Title: ALTDSE: An Arnoldi-Lanczos program to solve the time-dependent Schrödinger equation
Authors: Xiaoxu Guan, C.J. Noble, O. Zatsarinny, K. Bartschat, B.I. Schneider
Program title: ALTDSE
Catalogue identifier: AEDM_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 180(2009)2401
Programming language: Fortran 95. [A Fortran 2003 call to "flush" is used to simplify monitoring the output file during execution. If this function is not available, these statements should be commented out.].
Computer: Shared-memory machines.
Operating system: Linux, OpenMP.
Has the code been vectorised or parallelized?: Yes
RAM: Several Gb, depending on matrix size and number of processors
Supplementary material: To facilitate the execution of the program, Hamiltonian field-free and dipole matrix files are provided.
Keywords: Time-dependent Schrödinger equation, Arnoldi-Lanczos, attosecond intense laser-atom interactions.
PACS: 32.80.Fb, 32.80.Rm, 42.65.Re.
Classification: 2.5.

External routines: LAPACK, BLAS

Nature of problem:
We describe a computer program for a general ab initio and non-perturbative method to solve the time-dependent Schrödinger equation (TDSE) for the interaction of a strong attosecond laser pulse with a general atom [1,2]. The probabilities for survival of the initial state, excitation of discrete states, and single ionization due to multi-photon processes can be obtained.

Solution method:
The solution of the TDSE is propagated in time using the Arnoldi-Lanczos method. The field-free Hamiltonian and the dipole matrices, originally generated in an arbitrary basis (e.g., the flexible B-spline R-matrix (BSR) method with non-orthogonal orbitals [3]), must be provided in the eigenbasis of the problem as input.

Restrictions:
The present program is restricted to a 1Se initial state and linearly polarized light. This is the most common situation experimentally, but a generalization is straightforward.

Running time:
Several hours, depending on the number of threads used.

References:
[1] X. Guan, O. Zatsarinny, K. Bartschat, B. I. Schneider, J. Feist, and C. J. Noble, Phys. Rev. A 76, 053411 (2007).
[2] X. Guan, C. J. Noble, O. Zatsarinny, K. Bartschat, and B. I. Schneider, Phys. Rev. A 78, 053402 (2008).
[3] O. Zatsarinny, Comp. Phys. Commun. 174, 273 (2006).