The de‐excitation of vibrationally energetic Morse oscillators via impulsive collision with an atom is discussed. In certain types of atom–oscillator systems intramolecular vibration‐to‐rotation energy transfer is more important than intermolecular vibration‐to‐translation transfer. Since the efficiency of this intramolecular de‐excitation has a different dependence on particle mass and collision energy than does the intermolecular de‐excitation, restricting consideration to the latter, e.g., using a collinear collision model, does not always lead to an adequate description of the de‐excitation process.

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The smallest root is the value of ωt at the first intersection of the linear trajectory of A relative to B–C and the B–C oscillatory trajectory.
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This technique for calculation of oscillator phase and momentum at collision is an algebraic representation of the graphical method described in Ref. 2, and the comments therein are pertinent here, particularly the discussion of the “excluded phase” phenomenon.
10.
The calculated Δε(θ0) values for an atom‐Morse oscillator system with given masses and initial energies depend only on the dissociation energy D and are independent of α since pτ is independent of α [Eqs. (15) and (16)]. Similarly, for atom‐harmonic‐oscillator collisions the Δε(θ0) values are independent of the oscillator force constant.
11.
The calculated Δε values depend only on the relative masses, and not absolute values, so that mass units are arbitrary; the numerical values chosen here were assumed to be atomic mass units.
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This m̃ value is close to the maximum limiting value of unity for atom‐homonuclear‐oscillator systems.
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An analogous failure of the “fixed orientation” approach has been observed in exact calculations on collisional excitation of initially nonvibrating oscillators;
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