1
|
Ma L, Li D, Jiang P, Cheng M, Gao H. Strongly Rotationally Dependent Lifetimes of C 2 in the 2 3Σ g- State: Implications for Predissociation in the Vacuum Ultraviolet Region. J Phys Chem Lett 2024:8620-8627. [PMID: 39146524 DOI: 10.1021/acs.jpclett.4c01605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
The radiative and photodissociative properties of the dicarbon molecule, C2, in high-lying electronic states are of utmost importance for modeling the photochemical processes that occur in various astronomical environments. Despite extensive spectroscopic studies in the last two centuries, the photodissociation properties of C2 are still largely unknown, particularly for quantum states in the vacuum ultraviolet (VUV) region. Here, the lifetimes of C2 for each individual rovibrational level in the recently identified 23Σg- state are measured for the first time using a VUV-pump-UV-probe photoionization scheme. The lifetimes are found to be strongly dependent on the rotational and vibrational quantum levels in the 23Σg- state. The strongly rotationally dependent lifetimes observed here indicate that the 23Σg- state may mainly undergo a predissociation process through couplings with nearby repulsive electronic states. The current observation could have important applications in modeling the interstellar medium and cometary comae.
Collapse
Affiliation(s)
- Liying Ma
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Di Li
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Pan Jiang
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Min Cheng
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hong Gao
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| |
Collapse
|
2
|
Jiang P, Lu L, Liu M, Gao H. Multi-channel photodissociation dynamics of 14N 2 in its b' 1Σ+u( ν = 20) state. Phys Chem Chem Phys 2022; 24:11544-11551. [PMID: 35506911 DOI: 10.1039/d2cp01148d] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
b' 1Σ+u(ν = 20) is the first vibronic state above the dissociation limit N(2D3/2,5/2) + N(2D3/2,5/2) of 14N2 that has been observed in the absorption spectrum. It provides a unique opportunity for studying the multi-channel photodissociation dynamics of 14N2, particularly the competition between the spin-forbidden and spin-allowed photodissociation channels. Here, photofragment excitation (PHOFEX) and (1VUV + 1'UV) photoionization spectra of 14N2 in the b' 1Σ+u(ν = 20) state and the time-slice velocity-map ion (TS-VMI) images at each individual rotational levels are collected by using a vacuum ultraviolet (VUV) pump-VUV probe scheme. It is found that the spin-forbidden channels N(4S) + N(2D3/2,5/2) and N(4S) + N(2P1/2,3/2) are competitive with the spin-allowed channel N(2D3/2,5/2) + N(2D3/2,5/2) at low rotational levels, while quickly become undetectable as the rotational quantum number J increases. At high rotational levels, only the spin-allowed channel N(2D3/2,5/2) + N(2D3/2,5/2) can be observed, supporting previous theoretical modeling. Channel-resolved partial predissociation rate constants (PPRCs) are calculated by combining branching ratios in this study and total predissociation rate constants (TPRCs) from previous absorption spectroscopic measurements. PPRCs for dissociation into channels N(4S) + N(2D3/2,5/2) and N(4S) + N(2P1/2,3/2) are almost independent of J, while those of N(2D3/2,5/2) + N(2D3/2,5/2) show complicated rotational dependence. Possible coupling schemes between b' 1Σ+u(ν = 20) and the high lying 1Πu and 3Πu states are analyzed, which provides deep insight into the multi-channel photodissociation dynamics of 14N2 in a high energy range.
Collapse
Affiliation(s)
- Pan Jiang
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. .,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Liya Lu
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. .,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Min Liu
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. .,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hong Gao
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. .,University of Chinese Academy of Sciences, Beijing 100049, China
| |
Collapse
|
3
|
Gao H. Molecular photodissociation in the vacuum ultraviolet region: implications for astrochemistry and planetary atmospheric chemistry. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1861354] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Hong Gao
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| |
Collapse
|
4
|
Guan L, Jiang P, Zhang G, Yin T, Chi X, Bai Y, Cheng M, Gao H. Vacuum Ultraviolet Photodissociation Branching Ratios of 12C 16O, 13C 16O, and 12C 18O from 100500 to 102320 cm -1. J Phys Chem A 2020; 124:9382-9391. [PMID: 33146529 DOI: 10.1021/acs.jpca.0c08026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The C+ ion photofragment spectra and photodissociation branching ratios into the two energetically available channels, C(1D) + O(3P) and C(3P) + O(3P), have been obtained for the three CO isotopologues, 12C16O, 13C16O, and 12C18O, in the vacuum ultraviolet range 100500-102320 cm-1. The two vibronic states of 1Σ+ symmetry, F(3dσ) 1Σ+(υ' = 1) and J(4sσ) 1Σ+(υ' = 0), predominantly dissociate into the lowest channel C(3P) + O(3P) through interactions with the repulsive D'1Σ+ state. All three vibronic states of 1Π symmetry, E'1Π(υ' = 1, 2) and G(3dπ) 1Π(υ' = 0), dissociate into both of the channels above. The photodissociation branching ratios into the channel C(1D) + O(3P) for E'1Π(υ' = 1, 2) are found to be independent of both the rotational quantum number and e/f parity, while those for G(3dπ) 1Π(υ' = 0) strongly depend on the rotational quantum number, indicating very different predissociation pathways between the valence states E'1Π(υ' = 1, 2) and the Rydberg state G(3dπ) 1Π(υ' = 0). The potential energy curves of CO in the aforementioned energy range and below have recently been well constructed due to a series of interplays between high-resolution spectroscopic studies and theoretical calculations; the photodissociation branching ratios measured in this study can provide further benchmarks for future theoretical investigations which aim to understand the detailed predissociation dynamics of CO.
Collapse
Affiliation(s)
- Lichang Guan
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Pan Jiang
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guodong Zhang
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Tonghui Yin
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaoping Chi
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu Bai
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Min Cheng
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hong Gao
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| |
Collapse
|
5
|
Jiang P, Chi X, Zhang G, Yin T, Guan L, Cheng M, Gao H. Reinvestigation of the Rydberg W 1Π(ν = 1) level of 12C 16O, 13C 16O, and 12C 18O through rotationally dependent photodissociation branching ratio measurements. J Chem Phys 2020; 152:234308. [PMID: 32571069 DOI: 10.1063/5.0009931] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A recent high resolution photoabsorption study revealed that the Rydberg W1Π(ν = 1) level of carbon monoxide (CO) is perturbed by the valence E″1Π(ν = 0) level, and the predissociation linewidth shows drastic variation at the crossing point due to the interference effect [Heays et al., J. Chem. Phys. 141(14), 144311 (2014)]. Here, we reinvestigate the Rydberg W1Π(ν = 1) level for the three CO isotopologues, 12C16O, 13C16O, and 12C18O, by measuring the rotationally dependent photodissociation branching ratios. The C+ ion photofragment spectra obtained here reproduce the recent high resolution photoabsorption spectra very well, including the presence of the valence E″1Π(ν = 0) level. The photodissociation branching ratios into the spin-forbidden channel C(1D) + O(3P) show sudden increases at the crossing point between the W1Π(ν = 1) and E″1Π(ν = 0) levels, which is in perfect accordance with the drastic variation of the linewidth observed in the recent spectroscopic study. Further analysis reveals that the partial predissociation rate into the lowest channel C(3P) + O(3P) shows a much more prominent decrease at the crossing point, which is caused by the interference effect between the W1Π(ν = 1) and E″1Π(ν = 0) levels, than that into the spin-forbidden channel C(1D) + O(3P), and this is the reason of the sudden increase as observed in the photodissociation branching ratio measurements. We hope that the current experimental investigation will stimulate further theoretical studies, which could thoroughly address all the experimental observations in a quantitative way.
Collapse
Affiliation(s)
- Pan Jiang
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaoping Chi
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Guodong Zhang
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Tonghui Yin
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Lichang Guan
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Min Cheng
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Hong Gao
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| |
Collapse
|