Quantum State-Dependent Fragmentation Dynamics of D2S Molecules Following Excitation at Wavelengths â¼ 129.1 and â¼ 139.1 nm.
J Phys Chem A
; 128(38): 8111-8122, 2024 Sep 26.
Article
in En
| MEDLINE
| ID: mdl-39283291
ABSTRACT
The first high-resolution translational spectroscopy studies of D atom photoproducts following excitation to the Rydberg states of D2S are reported. Excitation at wavelengths λ â¼ 139.1 nm reveals an unusual 'inverse' isotope effect; the 1B1(3da1â2b1) Rydberg state of D2S predissociates much faster than its counterpart in H2S. This is attributed to accidental near resonance with a vibrationally excited level of a lower-lying, more heavily predissociated Rydberg state of D2S that boosts the probability of nonadiabatic coupling to the dissociation continuum with 1Aâ³ symmetry. Excitation at λ â¼ 129.1 nm populates the 1B1(4da1â2b1) Rydberg state, which predissociates more slowly and allows the study of ways in which the branching into different quantum states of the SD products varies with the choice of parent excited (JKaKc) level. All excited parent levels yield both ground (X) and electronically excited (A) state SD fragments. The former are distributed over a wide range of rovibrational (vâ³, Nâ³) levels, while the population of levels with low v' and high N' is favored in the latter. These trends reflect the topographies of the dissociative 1Aâ³ (1A') potential energy surfaces that correlate with the respective dissociation limits. Rotational motion about the b-inertial axis in the excited state molecule increases the relative yield of SD(A) products, consistent with dissociation by rotationally (Coriolis-) induced coupling from the photoexcited Rydberg level to the 1A' continuum. Molecules excited to the rotationless (JKaKc = 000) level also yield some SD(A) products, however, confirming the operation of a rival fragmentation pathway wherein photoexcited molecules decay by initial vibronic coupling to the 1Aâ³ continuum, with subsequent nonadiabatic coupling between the 1Aâ³ and 1A' continua enabling access to the D + SD(A) limit.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
J Phys Chem A
Journal subject:
QUIMICA
Year:
2024
Document type:
Article
Affiliation country:
China
Country of publication:
United States