Effects of Alkylation on Deviations from Lennard−Jones Collision Rates for Highly Excited Aromatic Molecules: Collisions of Methylated Pyridines with HOD

Abstract

Collision rates and energy transfer distributions are reported for HOD with highly vibrationally excited 2-methylpyridine (2-picoline, E = 38 310 cm(-1)) and 2,6-dimethylpyridine (2,6-lutidine, E = 38 700 cm(-1)). High resolution transient IR absorption is used measured to complete product state distributions of scattered HOD(000) molecules with E(rot) = 109 to 1331 cm(-1). Doppler-broadened line profiles characterize the depletion and appearance for HOD molecules due to collisions with hot donors and show that the product translational and rotational energy distributions are similar for both donors with DeltaE(rel) = 370 cm(-1) and DeltaE(rot) approximately 75 cm(-1). The energy transfer rate for picoline (E)/HOD is 2.5 times larger than the Lennard-Jones collision rate. The energy transfer rate for lutidine(E)/HOD is 3.2 times larger than the Lennard-Jones collision rate. Previous work ( Havey, Liu, Li, Elioff, and Mullin, J. Phys. Chem. A 2007, 111, 13321-9 ) reported similar energy transfer values for pyrazine/HOD collisions and an energy transfer rate that is 1.7 times the Lennard-Jones collision rate. The observed collision rates are discussed in terms of hydrogen bonding interactions between HOD and the aromatic donor molecules. Energy gain profiles for HOD are compared with those for H(2)O.

Full State-Resolved Energy Gain Profiles of CO2 (J = 2−80) from Collisions of Highly Vibrationally Excited Molecules. 1. Relaxation of Pyrazine (E = 37900 cm−1)

“…Lennard-Jones collision rates are commonly used to model molecular collisions and they should be valid for collisions of weakly interacting species such as CO 2 at 300 K. Caution must be used however for the case of strongly interacting species such as water. In other studies we have measured total appearance rates for scattered HOD molecules that are as much as 3.5 times larger than the Lennard-Jones collision rate. ,, For these systems, state-resolved scattering data indicate that anisotropy in the intermolecular potential plays an important role in quenching pathways involving water …”

“…In other studies we have measured total appearance rates for scattered HOD molecules that are as much as 3.5 times larger than the Lennard-Jones collision rate. 58,61,71 For these systems, state-resolved scattering data indicate that anisotropy in the intermolecular potential plays an important role in quenching pathways involving water. 58 2.…”

Non-statistical intermolecular energy transfer from vibrationally excited benzene in a mixed nitrogen-benzene bath

“…The time scale for energy transfer to molecular vibrational modes may determine whether molecular energy transfer is able to couple with acoustic modes that cause turbulence to occur in hypersonic boundary layers. [7][8][9] There have been several experimental studies of such dynamics, in which pathways for transfer of energy to bath molecules CO 2 , 10,11 H 2 O, [12][13][14][15][16] HOD, [17][18][19] and DCl 20 were investigated. a) Author to whom correspondence should be addressed: bill.hase@ttu.edu…”