Oscillations in the total photodetachment cross sections of a linear triatomic negative ion A Afaq ∗ Center of Excellence in Solid State Physics, University of the Punjab, Quid-e-Azam Campus, Lahore-54590, Pakistan M. Hanif, Iftikhar Ahmad † Department of Physics, Hazara University, Mansehra, Pakistan The total photodetachment cross section of a linear triatomic negative ion using plane polarized laser light parallel to the axis of the molecular ion is derived. The cross section shows strong oscillations in contrast to the recently reported case, where the laser polarization was perpendicular to the axis of the triatomic molecular ion (Appl. Phys. Lett. 94 , 041125, 2009). Closed orbit theory is used to explain these oscillations and the results are compared with a diatomic molecule. Interest in the photodetachment process and photodetachment spectroscopy has gown in the recent years [1–12]. The photodetachment cross section for hydrogen negative ion has been investi- gated experimentally [13, 14] and theoretically [15–23]. The most intrusting aspect of the H − cross section in the presence of a static electric field of a few hundred kV/cm above threshold, it shows oscillations while smooth in the absence of the field. Afaq and Du extended one-center model and developed two-center model for the photodetachment of electron from a diatomic molecule [2, 4, 5]. They gave the idea of special detached-electron orbit starting from one atom and ending at the other atom in a diatomic negative molecule. This special detached-electron orbit is responsible for the oscillations in the total photodetachment cross sections and is the updated version of the closed orbit theory [19, 24, 25]. Recently Afaq et al [1] showed a smooth behavior of the total photodetachment cross section of a linear triatomic negative ion placed perpendicular to the direction of polarization of the laser beam. The total cross section approaches one-center and two-center models for a highly energetic $^{∗}$Electronic address: draafaq@gmail.com $^{†}$Electronic address: ahma5532@gmail.com I. INTRODUCTION arXiv:1001.4183v1 [physics.atom-ph] 23 Jan 2010