Efficiency of energy transfer in protonated diglycine and dialanine SID - Effects of collision angle, peptide ion size, and intramolecular potential

Classical trajectory simulations are performed to study energy transfer in collisions of protonated diglycine, (gly)(2)H+, and dialanine, (ala)(2)H+, ions with the diamond {111} surface, for a collision energy E-i in the range of 5-110 eV and incident angles of 0 and 45degrees with respect to the surface normal. The distribution of energy transfer to vibrational/rotational degrees of freedom, DeltaE(int), and to the surface, DeltaE(surf), and of energy remaining in peptide ion translation, E-f, are very similar for (gly)(2)H+ and (ala)(2)H+. The average percent energy transferred to DeltaE(surf) and E-f increases and decreases, respectively, with increase in E-i. Average energy transfer to DeltaE(int) is less dependent on E-i, but does decrease with increase in E-i. The AMBER and AM1 models for the (gly)(2)H+ intramolecular potential give statistically identical energy transfer distributions in (gly)(2)H+ +diamond {111} collisions. A comparison of the current study with previous trajectory simulations of glyH(+), (gly)(3)H+, and (gly)(5)H+ collisions with diamond {111} shows that the energy transfer efficiencies to DeltaE(int), DeltaE(surf), and E-f are similar for (gly)(2)H+, n = 1-5. The energy transfer distributions for (gly)(2)H+ + diamond {111} collisions depend on the collision angle and do not scale in accord with the normal component of the collision energy E-i(n) for collisions with theta(i) of 0 and 45degrees. (C) 2003 Elsevier B.V. All rights reserved.