Transporting and concentrating vibrational energy to promote isomerization

Lau, Jascha A.; Chen, Li; Choudhury, Arnab; Schwarzer, Dirk; Verma, Varun B.; Wodtke, Alec M.

doi:10.1038/s41586-020-03081-y

Cited by 9 publications

(28 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[16] The fundamental difference in the lifetimes is attributed to different vibrational relaxation mechanisms that occur on the various types of substrates. Generally, relaxation can occur via excitation of electronic degrees of freedom (DOFs) (electron-hole-pairs) of the substrate and excitation of vibrational DOFs (phonons and frustrated adsorbate motions 1 ).…”

Section: Vibrational Relaxationmentioning

confidence: 99%

“…Furthermore, the rate constants depend on the squared transition dipole moments of the 𝑛 → 𝑛 + 1 and 𝑚 → 𝑚 − 1 transitions (𝜇 𝑛 + 1|𝑥|𝑛 and 𝜇 𝑚 − 1|𝑥|𝑚 , respectively). Another important result is that the rate constant of a one-phonon process, 𝑘 (1) 𝑛𝑚 , is proportional to 𝑅 −8 and therefore strongly distance-dependent.…”

Section: Co(𝑛) + Co(𝑚)mentioning

confidence: 99%

“…2.65 and 2.66, must be diagonalized. The eigenvalues of 𝐻 , Δ𝐸 (1) 𝑙 , can be related to the frequency shifts of the vibrational excitons relative to the frequency of the unperturbed molecules: .67) The eigenvectors of 𝐻 , C 𝑙 , define the expansion coefficients of the excitonic wavefunctions (Eq. ( .68) Within the oriented gas model (Eq.…”

Section: Static and Dynamic Frequency Shiftsmentioning

confidence: 99%

“…by "LIF"). This position overlaps with the focal point of a 30°off-axis parabolic mirror (reflected focal length: 54.5 mm), 1 which collects and collimates the fluorescence from the NaCl surface and directs it toward the monochromator. Two additional apertures in the parabolic mirror holder allow the pulses from the molecular source (see Section 3.1.5) to enter the cold shield.…”

Section: Snspd-based Mid-infrared Emission Spectrometermentioning

confidence: 99%

“…The group of Ertl studied the energetics of the individual steps of the ammonia synthesis on different iron surfaces and showed that the mechanism obtained from the experiments on single crystals could be related to the industrial reaction. [1] This example suggests that even reactions at complicated gas-surface systems can, in principle, be predicted if all relevant atomic scale processes are understood. [2] Molecular vibrations can have a strong influence on reactivity, as they are closely connected to the breaking and formation of chemical bonds.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Vibrational Energy Transfer Between CO Molecules on a NaCl(100) Surface Studied by Infrared Fluorescence Spectroscopy

Alexander¹

View full text Add to dashboard Cite

The breaking of chemical bonds in surface reactions is inherently connected to highly excited molecular vibrations. Therefore, understanding the vibrational energy transfer dynamics of adsorbed molecules, which effectively determine the lifetime of vibrational excitation, is of great importance. CO adsorbed on NaCl(100) is possibly the best studied physisorbed molecule. Despite that, most previous experiments have focused on the vibrational ground state and the 𝑣 = 0 → 1 transition of CO-mainly because dispersed fluorescence from high vibrational states could not be observed with conventional infrared detectors. In this thesis, I thus investigate the vibrational energy transfer dynamics of CO on NaCl(100) in highly vibrationally excited states up to 𝑣 = 30.Dispersed and time-resolved laser-induced fluorescence (LIF) is used to observe the vibrational dynamics. For this, an improved version of a recently developed mid-infrared emission spectrometer based on superconducting nanowire single-photon detectors (SNSPDs) is used. The current setup is capable of detecting infrared fluorescence from a single adsorbate layer with spectral and temporal resolution of 7 nm and ∼1 µs, respectively. High vibrational states, CO(𝑣), are prepared by pulsed infrared laser excitation of CO to 𝑣 = 1 at cryogenic temperatures around 7 K. Subsequent vibrational energy pooling (VEP), driven by the anharmonicity of the CO oscillators, concentrates many vibrational quanta in single molecules via vibration-to-vibration (V-V) energy transfer from the surrounding molecules: CO(n) + CO(m) → CO(n+1) + CO(m -1).Kinetic Monte Carlo simulations of the vibrational dynamics in a 13 C 18 O monolayer show that VEP proceeds via a sequential mechanism, in which adsorbates in high vibrational states are further excited by collecting vibrational quanta from molecules in lower vibrational states over increasingly large distances and timescales, up to 100 µs. The shape of the phonon spectrum, to which the excess energy in the V-V transfer processes is dissipated, causes a distinct peak structure in the vibrational state distribution. Furthermore, dissipation to transverse phonons that involve Na atom motion in the surface plane is found to be most effective. Vibrational relaxation to the NaCl substrate is slower than VEP and occurs on the millisecond time scale for 𝑣 ≤ 23. The 𝑣-dependent relaxation rates can be explained by a classical electrodynamic mechanism, whereby energy is transferred non-radiatively to the absorbing NaCl medium via the near-field of the oscillating CO dipole. This finding is in strong contrast to the dominating mechanism for more strongly bound adsorbates, where energy is dissipated via anharmonic couplings between the CO vibration and the surface phonons.The improved resolution of the emission spectrometer revealed a previously unknown metastable O-down orientation (Na + -OC), which is formed from the stable C-down v First and foremost, I would like to express my deepest gratitude to my supervisor Alec Wodtke for getting the chance...

show abstract

Section: Vibrational Relaxationmentioning

confidence: 99%

Section: Co(𝑛) + Co(𝑚)mentioning

confidence: 99%

Section: Static and Dynamic Frequency Shiftsmentioning

confidence: 99%

Section: Snspd-based Mid-infrared Emission Spectrometermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Vibrational Energy Transfer Between CO Molecules on a NaCl(100) Surface Studied by Infrared Fluorescence Spectroscopy

Alexander¹

View full text Add to dashboard Cite

show abstract

Manipulating tunnelling gateways in condensed phase isomerization

et al. 2023

Self Cite

View full text Add to dashboard Cite

When a chemical reaction occurs via tunnelling, a simple mass‐dependence is expected, where substitution of atoms by heavier isotopes leads to a reduced reaction rate. However, as shown in a recent study of CO orientational isomerization at the NaCl(1 0 0) interface, the lightest isotopologues need not exhibit the fastest tunnelling; for the CO/NaCl system, the non‐monotonic mass‐dependence is understood through a new picture of condensed phase tunnelling where the overall rate is dominated by a few pairs of reactant/product states. These state‐pairs – termed quantum gateways – gain dynamical importance through accidentally enhanced tunnelling probabilities, facilitated by a confluence of the energetic landscape underlying the reaction as well as the phonon bath of the surrounding medium. Here, we explore gateway tunnelling through measurements of the kinetic isotope effect for CO isomerization in a monolayer buried by many layers of either CO or N2. With an N2 overlayer, tunnelling rates are accelerated for all four isotopologues (12C16O, 13C16O, 12C18O and 13C18O), but the degree of acceleration is isotopologue‐specific and non‐intuitively mass dependent. A one‐dimensional tunnelling model involving an Eckart barrier cannot capture this behaviour. This reflects how a modification of the potential energy surface moves states in and out of resonance, thereby changing which tunnelling gateways can be accessed in the isomerization reaction. Key points The paper describes new systems that showcase resonance‐enhanced condensed phase tunnelling. Condensed phase tunnelling as described in this work may have implications for astrochemistry. A previously hypothesized mechanism is subjected to subsequent experimental scrutiny – the hypothesis stands the test.

show abstract

Spin-Forbidden Carbon–Carbon Bond Formation in Vibrationally Excited α-CO

DeVine¹,

Choudhury

Lau

et al. 2022

J. Phys. Chem. A

Self Cite

View full text Add to dashboard Cite

Fourier transform infrared spectroscopy of laser-irradiated cryogenic crystals shows that vibrational excitation of CO leads to the production of equal amounts of CO 2 and C 3 O 2 . The reaction mechanism is explored using electronic structure calculations, demonstrating that the lowest-energy pathway involves a spin-forbidden reaction of (CO) 2 yielding C( 3 P) + CO 2 . C( 3 P) then undergoes barrierless recombination with two other CO molecules forming C 3 O 2 . Calculated intersystem crossing rates support the spin-forbidden mechanism, showing subpicosecond spin-flipping time scales for a (CO) 2 geometry that is energetically consistent with states accessed through vibrational energy pooling. This spin-flip occurs with an estimated ∼4% efficiency; on the singlet surface, (CO) 2 reconverts back to CO monomers, releasing heat which induces CO desorption. The discovery that vibrational excitation of condensed-phase CO leads to spin-forbidden C–C bond formation may be important to the development of accurate models of interstellar chemistry.

show abstract

Transporting and concentrating vibrational energy to promote isomerization

Cited by 9 publications

References 34 publications

Vibrational Energy Transfer Between CO Molecules on a NaCl(100) Surface Studied by Infrared Fluorescence Spectroscopy

Vibrational Energy Transfer Between CO Molecules on a NaCl(100) Surface Studied by Infrared Fluorescence Spectroscopy

Manipulating tunnelling gateways in condensed phase isomerization

Spin-Forbidden Carbon–Carbon Bond Formation in Vibrationally Excited α-CO

Contact Info

Product

Resources

About