Fundamentals and Mechanisms of Resonance‐Enhanced Multiphoton Ionization (<scp>REMPI</scp>) in Vacuum and its Application in Molecular Spectroscopy

Boesl, U.; Zimmermann, Ralf

doi:10.1002/9783527682201.ch2

Cited by 4 publications

(3 citation statements)

References 142 publications

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“…Resonance-enhanced multiphoton ionization (REMPI) of molecules with an intense UV laser pulse, in combination with the detection of the charged products, is both sensitive and background-free [136]. The UV laser pulses can be derived from a frequency-converted, tunable dye laser, and a microchannel plate (MCP) can serve as a detector.…”

Section: Detectionmentioning

confidence: 99%

Dynamics of a buffer-gas-loaded, deep optical trap for molecules

Singh¹,

Maisenbacher²,

Lin³

et al. 2023

Preprint

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We describe an approach to optically trapping small, closed-shell molecules at cryogenic temperatures by buffer-gas loading a deep optical dipole trap. The ∼10 K trap depth will be produced by a tightlyfocused, 1064-nm cavity capable of reaching intensities of hundreds of GW/cm 2 . Molecules will be directly buffer-gas loaded into the trap using a helium buffer gas at 1.5 K. The very far-off-resonant, quasi-electrostatic trapping mechanism is insensitive to a molecule's internal state, energy level structure, and its electric and magnetic dipole moment. Here, we theoretically investigate the trapping and loading dynamics, as well as the heating and loss rates, and conclude that 10 4 -10 6 molecules are likely to be trapped. Our trap would open new possibilities in molecular spectroscopy, studies of cold chemical reactions, and precision measurement, amongst other fields of physics.

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Section: Detectionmentioning

confidence: 99%

Dynamics of a buffer-gas-loaded, deep optical trap for molecules

Singh¹,

Maisenbacher²,

Lin³

et al. 2023

Preprint

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“…Consequently, absorption cross sections of electronic transitions are directly involved in the ionization rate of the molecules. According to Boesl & Zimmermann (2021), for a low laser flux, the volume density of ions n + (in cm −3 ) produced by the REMPI process can be estimated using the following expression:…”

Section: Experimental Setup Descriptionmentioning

confidence: 99%

Ultraviolet electronic spectroscopy of heavily substituted naphthalene derivatives

Fréreux,

Godard,

Dartois

et al. 2023

A&A

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Context. The so-called bump spectral signature observable on interstellar extinction curves, peaking at 217.5 nm, is commonly assigned to π* ← π transitions from carbonaceous carriers, but the exact nature of the carbonaceous carriers remains debated. Aims. To constrain the chemical structures associated with the bump carriers, we record and compare the UV spectra of a large variety of carbonaceous molecules to this interstellar feature. Methods. Large carbonaceous molecules, such as polycyclic aromatic hydrocarbons (PAHs), were produced by a combustion process stabilized at low pressure under rich flame conditions. Species were extracted and probed through resonance enhanced multiphoton ionization spectroscopy coupled to a time-of-flight mass spectrometer. Masses and absorption profiles of the carbonaceous molecules were measured, and their spectra were compared to the bump feature. Results. Species showing a specific mass progression starting at mass 128 u visible up to mass 394 u with a characteristic progression of +14 u present a common electronic absorption band profile peaking asymptotically around 220 nm. The first masses were assigned to a naphthalene C10H8 molecule and two of its derivatives: C10H7CH3 and C10H7C2H5. The mass progression of +14 u is explained by successive H atom substitutions by CH3 functional groups. This mass distribution was thus assigned to naphthalene derivatives with large aliphatic carbon substitution. This derivative family shows an electronic band assigned to S3 ← S0 transitions involving electron promotion within the π aromatic orbitals of the naphathlene chromophore. More importantly, after a few substitutions, the position of the band converges asymptotically to a value close to the interstellar bump signature, independent of the molecule size. Conclusions. Based on the asymptotic behavior of the larger members in the species distribution, a similar band position is expected from double aromatic ring substructures within hydrogenated amorphous carbons (HACs). Similar to the conclusions of previous works, we find substituted naphthalene units as substructures of interstellar HACs to be good candidates as carriers of the bump feature.

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“…To tackle this challenge, we implemented resonance-enhanced multiphoton ionization (REMPI), a well-established technique known for its soft ionization capabilities and high ionization efficiencies, which can reach up to 10% (ref. 21). Specifically, we used [2 + 1] REMPI on 1,3-DBP to investigate the formation of cations and their subsequent structural changes.…”

mentioning

confidence: 99%

Capturing the generation and structural transformations of molecular ions

Heo,

Kim,

Segalina

et al. 2024

Nature

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Molecular ions are ubiquitous and play pivotal roles1–3 in many reactions, particularly in the context of atmospheric and interstellar chemistry4–6. However, their structures and conformational transitions7,8, particularly in the gas phase, are less explored than those of neutral molecules owing to experimental difficulties. A case in point is the halonium ions9–11, whose highly reactive nature and ring strain make them short-lived intermediates that are readily attacked even by weak nucleophiles and thus challenging to isolate or capture before they undergo further reaction. Here we show that mega-electronvolt ultrafast electron diffraction (MeV-UED)12–14, used in conjunction with resonance-enhanced multiphoton ionization, can monitor the formation of 1,3-dibromopropane (DBP) cations and their subsequent structural dynamics forming a halonium ion. We find that the DBP+ cation remains for a substantial duration of 3.6 ps in aptly named ‘dark states’ that are structurally indistinguishable from the DBP electronic ground state. The structural data, supported by surface-hopping simulations15 and ab initio calculations16, reveal that the cation subsequently decays to iso-DBP+, an unusual intermediate with a four-membered ring containing a loosely bound17,18 bromine atom, and eventually loses the bromine atom and forms a bromonium ion with a three-membered-ring structure19. We anticipate that the approach used here can also be applied to examine the structural dynamics of other molecular ions and thereby deepen our understanding of ion chemistry.

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Fundamentals and Mechanisms of Resonance‐Enhanced Multiphoton Ionization (REMPI) in Vacuum and its Application in Molecular Spectroscopy

Cited by 4 publications

References 142 publications

Dynamics of a buffer-gas-loaded, deep optical trap for molecules

Dynamics of a buffer-gas-loaded, deep optical trap for molecules

Ultraviolet electronic spectroscopy of heavily substituted naphthalene derivatives

Capturing the generation and structural transformations of molecular ions

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