Modification of Vibrational Parameters of a D∞h-Symmetric Triatomic Molecule in a Laser Plasma

Abstract

We estimate theoretically the strong-field-modified vibrational parameters of three-atomic ABA molecules with D∞h symmetry in a laser-induced plasma. The linear CO2 and CS2 molecules in the X1Σg state are considered as examples. We show that double degeneracy of the Πu mode is removed due to reduction of the ABA molecule symmetry by the laser field. The linear form of ABA molecule is preserved, the bond length being elongated.

Modification of Vibrational Parameters of a CO2 Molecule by a Laser Field: Impact on Tunnel Ionization

“…In ref. [14], it is shown that the relative change of the C-O bond length amounts to 0.43%, and that of the Ω y frequency is −1.0%, at the laser field intensity of 1.00 × 10 14 W/cm 2 .…”

“…The change in the vibrational parameters of the CO 2 molecule in the laser field (2) has been recently investigated in detail in ref. [14]. In the lowest order, this change is linear in the radiation intensity.…”

“…Indeed, the laser field violates the physical equivalence of mutually orthogonal vibrations of the Π u mode (see also Figure 1). Note that from Equation ( 24) it follows that C x = C y , S x = S y , i.e., the vibrational levels are not splitted at θ = 0 • , while at θ = 90 • their splitting is maximal and amounts to ∆Ω y /∆Ω x θ=90 • = 2.33 for CO 2 [14].…”

“…The laser-induced modification of vibrational parameters of linear triatomics possessing a higher D ∞h symmetry was studied in ref. [14]. On the examples of CO 2 and CS 2 , it was shown that, within the accuracy of ∼I, the geometry of these molecules are not influenced by the radiation.…”

“…In Section 2.2, we present the Born-Oppenheimer approximation and the Dyson orbital formalism to account for the internal structure of the molecular core. In Section 2.3, we present the general formalism developed in our papers [12,14] for the calculation of the laser-modified vibrational parameters and apply this formalism to the CO 2 molecule. In Section 2.4, a method is discussed for accounting for the excitation of internal degrees of freedom in the "inelastic tunnel effect" model [31].…”