Vibrational Energy Gain in the ν2 Bending Mode of Water via Collisions with Hot Pyrazine (Evib = 37900 cm-1): Insights into the Dynamics of Energy Flow

Abstract

Energy gain into specific rotational levels of vibrationally excited H2O(010) resulting from collisions with highly vibrationally excited pyrazine in a low-pressure, 298 K environment was investigated using high-resolution transient infrared absorption spectroscopy of water at λ ≈ 2.7 μm. Vibrationally excited pyrazine with 37900 cm-1 internal energy was generated by 266 nm optical excitation to an electronically excited singlet state of pyrazine, followed by rapid radiationless decay to the ground electronic state. Collisions between highly excited pyrazine and water that result in excitation of the ν2 bending vibrational mode (ν2 = 1594 cm-1) in water were studied by monitoring the time-resolved appearance of individual rotational states of H2O(010). Transient absorption signals were obtained for a number of rotational states with Erot ≤ 811 cm-1. The nascent distribution of rotational states for the scattered, vibrationally excited water molecules, H2O(010), is well characterized by a Boltzmann rotatio...