Fig. 1: Potential energy surfaces and S0/S1 quantum states of CH3ND2.
From: Tracking the structural change of the predissociating molecule near the transition state
a A schematic diagram showing the predissociation dynamics of the S1 CH3ND2. One-dimensional potential energy curves for the S0 and S1 states were calculated by scanning one of the N-D bond lengths of the otherwise frozen molecular geometry at the S1 minimum energy. Photoexcitation to the S1 state using single UV or IR + UV double resonance excitation initiates the N-D bond predissociation via tunneling through the reaction barrier on the adiabatic S1 surface. The inset shows the optimized geometry of CH3ND2 in the S0 (lower) or S1 (upper) state. Two different schemes of IR + UV double resonance excitations were employed; b The IR spectrum of the ground state was recorded by scanning the IR photon energy with the fixed UV wavelength of 243.069 nm. The experiment (black solid line) of the ν11″ band was completely reproduced by the asymmetric rotor simulation (red dashed line) with Trot = 3 K and a linewidth (Γ) of 1.0 cm−1. Rovibrational transitions with relative oscillator strengths are given as sticks. The red arrow depicts the rotational transition at 2984.0 cm−1 corresponding to the S0’ ( J’,Ka’) ← S0” ( J”,Ka”) transitions of (1,0) ← (1,1) and (2,1) ← (3,0). c The DR3PI spectrum was obtained by scanning the UV wavelength with the fixed IR laser at 2984.0 cm−1. d Progression of internal rotor states of which the rotation quantum numbers (m) were assigned from spectral simulations (see the text). Source data are provided as a Source Data file.
