(Color online) Variation of the (γ) of the electron with normalized distance (ξ): (a) For different orders of n (red, black and blue colors are for n = 1 , 2 and 3) with a 1 = 3 , a 2 = 2.4 , and ω p 0 = 0.3 ω 2 . (b) For different values of a 2 (red, black, and blue colors are for a 2 = 2 , 2.4, 2.8) with a 1 = 3 , n = 2 , and ω p 0 = 0.3 ω 2 , respectively, when relativistic and ponderomotive nonlinearities are operative.