Mode-specific vibrational predissociation dynamics of (HCl)2 via the free and bound HCl stretch overtones

Abstract

Velocity-map ion imaging has been used to study the vibrational predissociation dynamics of HCl dimer following IR excitation in the HCl stretch overtone region near 1.77 Å. HCl monomer predissociation products were detected state-selectively using 2+1 resonance-enhanced multiphoton ionization spectroscopy. The IR action spectrum show the free HCl stretch (2ν1), the bound HCl stretch (2ν2), and a combination band involving the intermolecular van der Waals stretching mode (2ν2+ν4). Fragment speed distributions extracted from ion images obtained for a range of HCl(v = 0, 1; J) levels following vibrational excitation on the 2ν1 and 2ν2 bands yield the correlated product pair distributions. All product pairs comprise HCl(v = 1) + HCl(v = 0) and show a strong propensity to minimize the recoil kinetic energy. Highly non-statistical and mode-dependent HCl product rotational distributions are observed, in contrast to that observed following stretch fundamental excitation. Predissociation lifetimes are also mode-dependent: excitation of the free HCl leads to τVP = 13±1 ns, while the bound stretch has a shorter lifetime τVP ≤ 6 ns. The dimer dissociation energy determined from energy conservation, D0 = 397±7 cm -1 , is slightly smaller than previously reported values. The results are discussed in the context of previous observations for (HF)2 and (HCl)2 after excitation of HX stretch fundamentals and models for vibrational predissociation.

Hydrogen-Bonded π Complexes between Phosphaethyne and Hydrogen Chloride

“…The second stable structure ( j-2 ) differs from j-1 mainly in the orientation of the hydrogen-bonded HCl dimer, and the weak Cl···H–C hydrogen bond is absent, leading to a decreased binding energy of 21.8 kJ mol –1 . The dimeric HCl units in these two complexes resemble the structure of the extensively explored free HCl dimer. , The least stable structure ( j-3 ) is nonplanar with an overall C s symmetry, and it can be formally viewed as a result of complexation with a second HCl to HCP···HCl through additional Cl–H···π interaction.…”

“…The dimeric HCl units in these two complexes resemble the structure of the extensively explored free HCl dimer. 57,58 The least stable structure (j-3) is nonplanar with an overall C s symmetry, and it can be formally viewed as a result of complexation with a second HCl to HCP•••HCl through additional Cl−H•••π interaction.…”

Fragment imaging in the infrared photodissociation of the Ar-tagged protonated water clusters H3O+–Ar and H+(H2O)2–Ar

“…Since their pioneering work, state-specific predissociation dynamics has extensively been investigated for hydrogen-bonded clusters. [25][26][27][28][29] However, there is a general difficulty in the gas-phase experiments on neutral systems regarding the size selection of target clusters. Though there are a few techniques for the size selection of neutrals, for example the rare-gas scattering method, 4 a versatile technique that can be easily employed in experiments to investigate the dynamics has not been established thus far.…”