Direct measurement of the binding energy of the NO dimer

Abstract

The binding energy of the NO dimer has been measured directly using velocity-mapped ion imaging. NO dimer is photodissociated to produce NO(X) and NO(A), and the NO(A) is then nonresonantly ionized to NO+. The threshold for production of NO+ ions is measured at 44 893±2 cm−1, which corresponds to a binding energy of 696±4 cm−1.

Infrared combination and difference bands of the NO dimer

“…This effect can be understood in relation to the fact that excitation of m 5 causes the intermolecular bond to strengthen, as demonstrated by the observation that m 5 (1789 cm À1 ) is significantly red-shifted compared to the NO monomer stretch frequency (1876 cm À1 ). Thus in the m 5 excited state the NO dimer binding energy increases to about 783 cm À1 compared to its ground state value [1] of about 696 cm À1 . It seems natural that this bond strengthening could lead to increases of the intermolecular vibrational frequencies.…”

“…We propose a new assignment for m 4 , the most elusive fundamental vibration of (NO) 2 . We also examine the N-O stretching overtone bands, 2m 5 , m 1 + m 5 , and 2m 1 , pointing out a possible small error in a previously reported [2] band origin of 2m 5 and suggesting a tentative first value for the origin of 2m 1 . The collected information on NO dimer vibrational states (a total of 19 vibrational origins) is discussed in terms of the molecular force field.…”

“…We now know that the dimer binding energy is almost 700 cm À1 [1,2], which is considerably greater than that for the dimer of a closedshell, but otherwise similar molecule, for example (CO) 2 with D 0 % 100 cm À1 [3]. We also know that (NO) 2 has a singlet ground electronic state with a cis-planar structure, C 2m symmetry, an N-N distance of about 2.26 Å , an N-O distance of about 1.15 Å , and an N-N-O angle of 97°.…”

Oxidation of a Water-Soluble Phosphine and Some Spectroscopic Probes with Nitric Oxide and Nitrous Acid in Aqueous Solutions

“…In the meantime, the binding energy for (NO) 2 in the gas phase has been reported as only 696 cm -1 , 40 again suggesting that the equilibrium concentration of N 2 O 2 in NO is extremely small and would require an exceptionally large rate constant, ∼1 Â 10 5 M -1 s -1 , for the (NO) 2 /PPh 3 reaction to explain the experimental data. On this basis, the (NO) 2 route would seem to be disfavored.…”

Hydrogen Bonding in Aromatic Alcohol-Water Clusters: A Brief Review

“…In the present review we discuss recent advances on the understanding of hydrogen bonding in aromatic alcoholwater clusters. Experimental measurements and theoretical calculations of the structure, binding energy, 25,26 and infrared frequency of phenol-water, benzyl alcohol-water, substituted phenol-water, β-naphthol-water and tropolone-water clusters are reviewed. Elucidation of the nature of hydrogen bonding in these clusters by the analysis of the shifts in the vibronic bands observed by spectroscopic techniques is exemplified.…”