Publications (2024)
Total peer-reviewed articles: 132
Absolute control over the quantum yield of a photodissociation reaction mediated by nonadiabatic couplings
Authors: Sola, Ignacio R.; Garcia-Vela, Alberto
Journal: CHEMICAL SCIENCE
Publication date: 2024/09/25
DOI: 10.1039/d4sc03235g
Abstract: Control of molecular reaction dynamics with laser pulses has been developed in the last decades. Among the different magnitudes whose control has been actively pursued, the branching ratio between different product channels constitutes the clearest signature of quantum control. In polyatomic molecules, the dynamics in the excited state is quagmired by non-adiabatic couplings, which are not directly affected by the laser, making control over the branching ratio a very demanding challenge. Here we present a control scheme for the CH3I photodissociation in the A band, that modifies the quantum yield of the two fragmentation channels of the process. The scheme relies on the optimized preparation of an initial superposition of vibrational states in the ground potential, which further interfere upon the excitation with a broad pump pulse. This interference can suppress any of the channels, regardless of its dominance, and can be achieved over the whole spectral range of the A band. Furthermore, it can be accomplished without strong fields or direct intervention during the dynamics in the excited states: the whole control is predetermined from the outset. The present work thus opens the possibility of extensive and universal control of the channel branching ratio in complex photodissociation processes. Control of molecular reaction dynamics with laser pulses has been developed in the last decades. The role of the initial wave function is now being unraveled.
Separation of oxygen from nitrogen using a graphdiyne membrane: a quantum-mechanical study
Authors: Rafiei, Maryam A.; Campos-Martinez, Jose; Bartolomei, Massimiliano; Pirani, Fernando; Maghari, Ali; Hernandez, Marta I.
Journal: PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Publication date: 2024/09/25
DOI: 10.1039/d4cp02287d
Abstract: Efficient separation of oxygen and nitrogen from air is a process of great importance for many industrial and medical applications. Two-dimensional (2D) membranes are very promising materials for separation of gases, as they offer enhanced mass transport due to their smallest atomic thickness. In this work, we examine the capacity of graphdiyne (GDY), a new 2D carbon allotrope with regular subnanometric pores, for separating oxygen (16O2) from nitrogen (14N2). A quantum-mechanical model has been applied to the calculation of the transmission probabilities and permeances of these molecules through GDY using force fields based on accurate electronic structure computations. It is found that the 16O2/14N2 selectivity (ratio of permeances) is quite high (e.g., about 106 and 102 at 100 and 300 K, respectively), indicating that GDY can be useful for separation of these species, even at room temperature. This is mainly due to the N2 transmission barrier (similar to 0.37 eV) which is considerably higher than the O2 one (similar to 0.25 eV). It is also found that molecular motions are quite confined inside the GDY pores and that, as a consequence, quantum effects (zero-point energy) are significant in the studied processes. Finally, we explore the possibility of 18O2/16O2 isotopologue separation due to these mass-dependent quantum effects, but it is found that the process is not practical since reasonable selectivities are concomitant with extremely small permeances. Graphdiyne promises a large selectivity for the separation of oxygen and nitrogen from air.
Deciphering the imprint of active galactic nucleus feedback in Seyfert galaxies: Nuclear-scale molecular gas deficits
Authors: Garcia-Burillo, S.; Hicks, E. K. S.; Alonso-Herrero, A.; Pereira-Santaella, M.; Usero, A.; Querejeta, M.; Gonzalez-Martin, O.; Delaney, D.; Almeida, C. Ramos; Combes, F.; Angles-Alcazar, D.; Audibert, A.; Bellocchi, E.; Davies, R. I.; Davis, T. A.; Elford, J. S.; Garcia-Bernete, I.; Honig, S.; Labiano, A.; Leist, M. T.; Levenson, N. A.; Lopez-Rodriguez, E.; Mercedes-Feliz, J.; Packham, C.; Ricci, C.; Rosario, D. J.; Shimizu, T.; Stalevski, M.; Zhang, L.
Journal: ASTRONOMY & ASTROPHYSICS
Publication date: 2024/09/24
DOI: 10.1051/0004-6361/202450268
Abstract: We study the distribution of cold molecular gas in the circumunuclear disks (CND; r <= 200 pc) of a sample of 64 nearby (D-L = 7 - 45 Mpc) disk galaxies - including 45 active galactic nuclei (AGN) and 19 nonAGN - for which high-spatial-resolution (median value similar or equal to 36 pc) multiline CO interferometer observations have been obtained at millimeter wavelengths with the Atacama Large Millimeter Array (ALMA) and/or Plateau de Bure Interferometer (PdBI). We decipher whether or not the concentration and normalized radial distribution of cold molecular gas change as a function of X-ray luminosity in the 2-10 keV range (L-X) in order to analyze the imprint left by AGN feedback. We also look for similar trends in the concentration and normalized radial distribution of the hot molecular gas and in the hot-to-cold-molecular gas mass ratio in a subset of 35 galaxies using near-infrared (NIR) integral field spectroscopy data obtained for the H-2 1-0 S(1) line. We find a significant turnover in the distribution of the cold molecular gas concentration as a function of X-ray luminosity with a breakpoint that divides the sample into two branches: (1) the AGN build-up branch (L-X <= 10(41.5 +/- 0.3) erg s(-1)) and (2) the AGN feedback branch (L-X >= 10(41.5 +/- 0.3) erg s(-1)). Lower-luminosity AGN and nonAGN of the AGN build-up branch show high cold molecular gas concentrations and centrally peaked radial profiles on nuclear (r <= 50 pc) scales. Higher-luminosity AGN of the AGN feedback branch show a sharp decrease in the concentration of molecular gas and flat or inverted radial profiles. The cold molecular gas concentration index (CCI) - defined as the ratio of surface densities at r <= 50 pc (Sigma(gaz)(50)) and r <= 200 pc Sigma(gaz)(200)), namely CCI equivalent to log(10)(Sigma(gaz)(50)/Sigma(gaz)(200))) - spans a 0.63 dex range, equivalent to a factor similar or equal to 4-5, between the galaxies lying at the high end of the AGN build-up branch and the galaxies showing the most extreme nuclear-scale molecular gas deficits in the AGN feedback branch. The concentration and radial distributions of the hot molecular gas in our sample follow qualitatively similar but less extreme trends as a function of X-ray luminosity. As a result, we find higher values of hot-to-cold molecular gas mass ratios on nuclear scales in the highest luminosity AGN sources of the AGN feedback branch. These observations confirm - with a three times larger sample - previous evidence found in the context of the Galaxy Activity Torus and Outflow Survey (GATOS) that the imprint of AGN feedback on the CND-scale distribution of molecular gas is more extreme in higher luminosity Seyfert galaxies of the local Universe.
GATOS: missing molecular gas in the outflow of NGC 5728 revealed by JWST
Authors: Davies, R.; Shimizu, T.; Pereira-Santaella, M.; Alonso-Herrero, A.; Audibert, A.; Bellocchi, E.; Boorman, P.; Campbell, S.; Cao, Y.; Combes, F.; Delaney, D.; Diaz-Santos, T.; Eisenhauer, F.; Esparza Arredondo, D.; Feuchtgruber, H.; Foerster Schreiber, N. M.; Fuller, L.; Gandhi, P.; Garcia-Bernete, I.; Garcia-Burillo, S.; Garcia-Lorenzo, B.; Genzel, R.; Gillessen, S.; Gonzalez Martin, O.; Haidar, H.; Hermosa Munoz, L.; Hicks, E. K. S.; Hoenig, S.; Imanishi, M.; Izumi, T.; Labiano, A.; Leist, M.; Levenson, N. A.; Lopez-Rodriguez, E.; Lutz, D.; Ott, T.; Packham, C.; Rabien, S.; Ramos Almeida, C.; Ricci, C.; Rigopoulou, D.; Rosario, D.; Rouan, D.; Santos, D. J. D.; Shangguan, J.; Stalevski, M.; Sternberg, A.; Sturm, E.; Tacconi, L.; Villar Martin, M.; Ward, M.; Zhang, L.
Journal: ASTRONOMY & ASTROPHYSICS
Publication date: 2024/09/20
DOI: 10.1051/0004-6361/202449875
Abstract: The ionisation cones of NGC 5728 have a deficit of molecular gas based on millimetre observations of CO (2-1) emission. Although photoionisation from the active nucleus may lead to suppression of this transition, warm molecular gas can still be present. We report the detection of eight mid-infrared rotational H-2 lines throughout the central kiloparsec, including the ionisation cones, using integral field spectroscopic observations with JWST/MIRI MRS. The H-2 line ratios, characteristic of a power-law temperature distribution, indicate that the gas is warmest where it enters the ionisation cone through disk rotation, suggestive of shock excitation. In the nucleus, where the data can be combined with an additional seven ro-vibrational H-2 transitions, we find that moderate velocity (30 km s(-1)) shocks in dense (10(5) cm(-3)) gas, irradiated by an external UV field (G(0) = 10(3)), do provide a good match to the full set. The warm molecular gas in the ionisation cone that is traced by the H-2 rotational lines has been heated to temperatures > 200 K. Outside of the ionisation cone the molecular gas kinematics are undisturbed. However, within the ionisation cone, the kinematics are substantially perturbed, indicative of a radial flow, but one that is quantitatively different from the ionised lines. We argue that this outflow is in the plane of the disk, implying a short 50 pc acceleration zone up to speeds of about 400 km s(-1) followed by an extended deceleration over similar to 700 pc where it terminates. The deceleration is due to both the radially increasing galaxy mass, and mass-loading as ambient gas in the disk is swept up.
The role of Na decoration on the hydrogen adsorption on coronene: A combined experimental and computational study
Authors: Garcia-Arroyo, Esther; Reider, Anna Maria; Kollotzek, Siegfried; Foitzik, Florian; Campos-Martinez, Jose; Bartolomei, Massimiliano; Pirani, Fernando; Hernandez, Marta I.; Mella, Massimo; Scheier, Paul
Journal: INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
Publication date: 2024/09/19
DOI: 10.1016/j.ijhydene.2024.07.425
Abstract: Functionalizing carbon-based materials with metal atoms has been proposed as an effective method to enhance the adsorption of hydrogen molecules on these substrates, thereby developing new useful systems for hydrogen storage. In this work, we investigate both experimentally and theoretically the role of sodium atom decoration on hydrogen attachment to coronene, a polycyclic aromatic hydrocarbon considered the smallest prototype of graphene. In the experiments, multiply charged helium nanodroplets are produced and exposed to sodium, coronene and hydrogen vapors, leading to the formation, within equal conditions, of clusters of hydrogen molecules surrounding bare and sodium-decorated protonated coronene, [H-coronene]+ + and [H-coroneneNa]+, + , respectively, whose abundances are accurately measured via mass spectrometry. These clusters are studied computationally by means of quantum Monte Carlo methods, using analytical representations of the H2 2-substrate interaction potentials based on high-level electronic structure calculations. It is found that the number of H2 2 molecules attached to both [H-coronene]+ + and [H-coronene-Na]+ + decreases as the evaporation pressure in the H2 2 chamber increases; however, the Na-decorated support retains a considerably larger number of molecules than the undecorated one, which is related to the higher evaporation energies of H2 2 molecules attached to the decorated support. In addition, most of the anomalies observed in the distributions of ion abundances vs. the number of hydrogen molecules have been identified in the theory as particularly stable clusters. For the Na-decorated substrate, it is found that clusters formed by four H2 2 molecules surrounding Na are very stable and that with the addition of two more molecules, the alkali atom becomes solvated.
Rotational spectra of five cyano derivatives of fluorene
Authors: Cabezas, Carlos; Janeiro, Jesus; Steber, Amanda L.; Perez, Dolores; Bermudez, Celina; Guitian, Enrique; Lesarri, Alberto; Cernicharo, Jose
Journal: PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Publication date: 2024/09/18
DOI: 10.1039/d4cp01924e
Abstract: The recent interstellar detection of individual polycyclic aromatic hydrocarbons (PAHs) in the dense molecular cloud TMC-1 brings interest in related species that could be present in this astronomical environment. These detections, that include pure PAHs and their cyano-derivative counterparts, were performed through the interplay between laboratory rotational spectroscopy experiments and radioastronomical observations. Here, we present the laboratory rotational spectroscopic study of the five cyano-derivatives of the PAH fluorene (C13H10). The samples for these five species were synthetized in the laboratory and then characterized in the gas phase using a chirped-pulse Fourier-transform microwave spectrometer operating between 2 and 12 GHz. The analysis of the rotational spectra allowed us to derive accurate molecular constants for the five isomers used to obtain frequency predictions that enable astronomical searches of these molecules in the interstellar medium. Fourier transform microwave spectra for the five cyano derivative isomers of the PAH fluorene have been observed in the 2-12 GHz frequency region.
Toolbox for nonreciprocal dispersive models in circuit quantum electrodynamics
Authors: Labarca, Lautaro; Benhayoune-Khadraoui, Othmane; Blais, Alexandre; Parra-Rodriguez, Adrian
Journal: PHYSICAL REVIEW APPLIED
Publication date: 2024/09/16
DOI: 10.1103/PhysRevApplied.22.034038
Abstract: We provide a systematic method for constructing effective dispersive Lindblad master equations to describe weakly anharmonic superconducting circuits coupled by a generic dissipationless nonreciprocal linear system, with effective coupling parameters and decay rates written in terms of the immittance parameters characterizing the coupler. This article extends the foundational work of Solgun et al. [IEEE Trans. Microw. Theory Techn. 67, 928 (2019)] for linear reciprocal couplers described by an impedance response. Notably, we expand the existing toolbox to incorporate nonreciprocal elements, account for direct stray coupling between immittance ports, circumvent potential singularities, and include collective dissipative effects that arise from interactions with external common environments. We illustrate the use of our results with a circuit of weakly anharmonic Josephson junctions coupled to a multiport nonreciprocal environment and a dissipative port. The results obtained here can be used for the design of complex superconducting quantum processors with nontrivial routing of quantum information, as well as analog quantum simulators of condensed matter systems.
Scalable multiphoton generation from cavity-synchronized single-photon sources
Authors: Li, Ming; Garcia-Ripoll, Juan Jose; Ramos, Tomas
Journal: PHYSICAL REVIEW RESEARCH
Publication date: 2024/09/13
DOI: 10.1103/PhysRevResearch.6.033295
Abstract: We propose an efficient, scalable, and deterministic scheme to generate multiple indistinguishable photons over independent channels, on demand. Our design relies on multiple single-photon sources, each coupled to a waveguide, all interacting with a common cavity mode. The cavity synchronizes and triggers the simultaneous emission of one photon by each source, which are collected by the waveguides. In a state-of-the-art circuit QED implementation, this scheme supports the creation of single photons with 99% purity, indistinguishability, and efficiency at rates of MHz. We also discuss conditions to produce up to 100 photons simultaneously with generation rates of hundreds of kHz. This is orders of magnitude more efficient than previous demultiplexed sources for boson sampling and enables the realization of deterministic multiphoton sources and scalable quantum information processing with photons.
Multiplexed quantum state transfer in waveguides
Authors: Penas, Guillermo F.; Puebla, Ricardo; Garcia-Ripoll, Juan Jose
Journal: PHYSICAL REVIEW RESEARCH
Publication date: 2024/09/13
DOI: 10.1103/PhysRevResearch.6.033294
Abstract: In this article, we consider a realistic waveguide implementation of a quantum network that serves as a testbed to show how to maximize the storage and manipulation of quantum information in QED setups. We analyze two approaches using wavepacket engineering and quantum state transfer protocols. First, we propose and design a family of orthogonal photons in the time domain. These photons allow for a selective interaction with distinct targeted qubits. Yet, mode multiplexing employing resonant nodes is largely spoiled by cross-talk effects. This motivates the second approach, namely, frequency multiplexing. Here we explore the limits of frequency multiplexing through the waveguide, analyzing its capabilities to host and faithfully transmit photons of different frequencies within a given bandwidth. We perform detailed one- and two-photon simulations and provide theoretical bounds for the fidelity of coherent quantum state transfer protocols under realistic conditions. Our results show that state-of-the-art experiments can employ dozens of multiplexed photons with global fidelities fulfilling the requirements imposed by fault-tolerant quantum computing. This is with the caveat that the conditions for single-photon fidelity are met.
Sodium into ?-Graphyne Multilayers: An Intercalation Compound for Anodes in Metal-Ion Batteries
Authors: Bartolomei, Massimiliano; Giorgi, Giacomo
Journal: ACS MATERIALS LETTERS
Publication date: 2024/09/12
DOI: 10.1021/acsmaterialslett.4c01119
Abstract: The bulk synthesis of gamma-graphyne has been recently achieved and evidenced a multilayered structure, which suggests its potential exploitation as a substitute of graphite-based anode materials for metals heavier than lithium (Li). In fact, each of its regular pores of sub-nanometric size features an optimal environment for hosting a single sodium (Na) ion, as reported here by means of accurate electronic structure calculations. We show that the graphyne/Na ion coupling mimics that found on the graphene/Li ion in terms of metal-single layer interaction and equilibrium distance. More importantly, in contrast to what is found for graphite, we demonstrate that graphyne intercalation compounds with Na are thermodynamically stable and feature an optimal storage capacity of 372 mAhg(-1). These findings, together with a limited crystal structure expansion upon Na intercalation, a low metal diffusion barrier as well as high electrical conductivity, pave the way to the development of novel graphyne-based anodes for efficient Na-ion batteries.
Stable collective charging of ultracold-atom quantum batteries
Authors: Rojo-Francas, Abel; Isaule, Felipe; Santos, Alan C.; Julia-Diaz, Bruno; Zinner, Nikolaj Thomas
Journal: PHYSICAL REVIEW A
Publication date: 2024/09/06
DOI: 10.1103/PhysRevA.110.032205
Abstract: We propose a quantum battery realized with a few interacting particles in a three-well system with different on-site energies, which could be realized with ultracold-atom platforms. We prepare the initial state in the lowest-energy well and charge the battery using a spatial-adiabatic-passage-based protocol, enabling the population of a higher-energy well. We examine the charging under varying interaction strengths and reveal that the consideration of collective charging results in an intriguing oscillatory behavior of the final charge for finite interactions, through diabatic evolution. Our findings provide an opportunity for building stable and controllable quantum batteries.
Geometrical description and Faddeev-Jackiw quantization of electrical networks
Authors: Parra-Rodriguez, A.; Egusquiza, I. L.
Journal: QUANTUM
Publication date: 2024/09/05
Abstract: In lumped-element electrical circuit theory, the problem of solving Maxwell’s equations in the presence of media is reduced to two sets of equations, the constitutive equations encapsulating local geometry and dynamics of a confined energy density, and the Kirchhoff equations enforcing conservation of charge and energy in a larger, topological, scale. We develop a new geometric and systematic description of the dynamics of general lumped-element electrical circuits as first order differential equations, derivable from a Lagrangian and a Rayleigh dissipation function. Through the Faddeev-Jackiw method we identify and classify the singularities that arise in the search for Hamiltonian descriptions of general networks. The core of our solution relies on the correct identification of the reduced manifold in which the circuit state is expressible, e.g., a mix of flux and charge degrees of freedom, including the presence of compact ones. We apply our fully programmable method to obtain (canonically quantizable) Hamiltonian descriptions of nonlinear and nonreciprocal circuits which would be cumbersome/singular if pure node-flux or loop-charge variables were used as a starting configuration space. We also propose a specific assignment of topology for the branch variables of energetic elements, that when used as input to the procedure gives results consistent with classical descriptions as well as with spectra of more involved quantum circuits. This work unifies diverse existent geometrical pictures of electrical network theory, and will prove useful, for instance, to automatize the computation of exact Hamiltonian descriptions of superconducting quantum chips.
Microsolvation of a Proton by Ar Atoms: Structures and Energetics of ArnH+ Clusters
Authors: de Oca-Estevez, Maria Judit Montes; Prosmiti, Rita
Journal: MOLECULES
Publication date: 2024/09/01
DOI: 10.3390/molecules29174084
Abstract: We present a computational investigation on the structural arrangements and energetic stabilities of small-size protonated argon clusters, ArnH+. Using high-level ab initio electronic structure computations, we determined that the linear symmetric triatomic ArH+ Ar ion serves as the molecular core for all larger clusters studied. Through harmonic normal-mode analysis for clusters containing up to seven argon atoms, we observed that the proton-shared vibration shifts to lower frequencies, consistent with measurements in gas-phase IRPD and solid Ar-matrix isolation experiments. We explored the sum-of-potentials approach by employing kernel-based machine-learning potential models trained on CCSD(T)-F12 data. These models included expansions of up to two-body, three-body, and four-body terms to represent the underlying interactions as the number of Ar atoms increases. Our results indicate that the four-body contributions are crucial for accurately describing the potential surfaces in clusters with n> 3. Using these potential models and an evolutionary programming method, we analyzed the structural stability of clusters with up to 24 Ar atoms. The most energetically favored ArnH+ structures were identified for magic size clusters at n = 7, 13, and 19, corresponding to the formation of Ar-pentagon rings perpendicular to the ArH+Ar core ion axis. The sequential formation of such regular shell structures is compared to ion yield data from high-resolution mass spectrometry measurements. Our results demonstrate the effectiveness of the developed sum-of-potentials model in describing trends in the nature of bonding during the single proton microsolvation by Ar atoms, encouraging further quantum nuclear studies.
SF6 Negative Ion Formation in Charge Transfer Experiments
Authors: Kumar, Sarvesh; Hoshino, Masamitsu; Kerkeni, Boutheina; Garcia, Gustavo; Ouerfelli, Ghofrane; Al-Mogren, Muneerah Mogren; Limao-Vieira, Paulo
Journal: MOLECULES
Publication date: 2024/09/01
DOI: 10.3390/molecules29174118
Abstract: In the present work, we report an update and extension of the previous ion-pair formation study of Hubers, M.M.; Los, J. Chem. Phys. 1975, 10, 235-259, noting new fragment anions from time-of-flight mass spectrometry. The branching ratios obtained from the negative ions formed in K + SF6 collisions, in a wide energy range from 10.7 up to 213.1 eV in the centre-of-mass frame, show that the main anion is assigned to SF5- and contributing to more than 70% of the total ion yield, followed by the non-dissociated parent anion SF6- and F-. Other less intense anions amounting to <20% are assigned to SF3- and F-2(-), while a trace contribution at 32u is tentatively assigned to S- formation, although the rather complex intramolecular energy redistribution within the temporary negative ion is formed during the collision. An energy loss spectrum of potassium cation post-collision is recorded showing features that have been assigned with the help of theoretical calculations. Quantum chemical calculations for the lowest-lying unoccupied molecular orbitals in the presence of a potassium atom are performed to support the experimental findings. Apart from the role of the different resonances participating in the formation of different anions, the role of higher-lying electronic-excited states of Rydberg character are noted.
PDRs4All X. ALMA and JWST detection of neutral carbon in the externally irradiated disk d203-506: Undepleted gas-phase carbon
Authors: Goicoechea, J. R.; Le Bourlot, J.; Black, J. H.; Alarcon, F.; Bergin, E. A.; Berne, O.; Bron, E.; Canin, A.; Chapillon, E.; Chown, R.; Dartois, E.; Gerin, M.; Habart, E.; Haworth, T. J.; Joblin, C.; Kannavou, O.; Le Petit, F.; Onaka, T.; Peeters, E.; Pety, J.; Roueff, E.; Sidhu, A.; Schroetter, I.; Tabone, B.; Tielens, A. G. G. M.; Trahin, B.; van de Putte, D.; Vicente, S.; Zannese, M.
Journal: ASTRONOMY & ASTROPHYSICS
Publication date: 2024/08/30
DOI: 10.1051/0004-6361/202450988
Abstract: The gas-phase abundance of carbon, xC = [C /H] gas = xC + + xC0 + xCO + : : :, and its depletion factors are essential parameters for understanding the gas and solid compositions that are ultimately incorporated into (exo)planets. The majority of protoplanetary disks are born in clusters and, as a result, are exposed to external far-ultraviolet (FUV) radiation. These FUV photons potentially a ffect the disk’s evolution, chemical composition, and line excitation. We present the first detection of the [C i] 609 -m fine-structure (3P1-3P0) line of neutral carbon (C0), achieved with ALMA, toward one of these disks, d203-506, in the Orion Nebula Cluster. We also report the detection of [C i] forbidden and C i permitted lines (from electronically excited states up to -10 eV) observed with JWST in the near-infrared (NIR). These lines trace the irradiated outer disk and photo-evaporative wind. Contrary to the common belief that these NIR lines are C+ recombination lines, we find that they are dominated by FUV-pumping of C0 followed by fluorescence cascades. They trace the transition from atomic to molecular gas, and their intensities scale with G0. The lack of outstanding NIR O i fluorescent emission, however, implies a sharper attenuation of external FUV radiation with E & 12 eV (. Lyman-fi). This is related to a lower e ffective FUV dust absorption cross section compared to that of interstellar grains, implying a more prominent role for FUV shielding by the C0 photoionization continuum. The [C i] 609 -m line intensity is proportional to N(C0) and can be used to infer xC. We derive xC ‘ 1.4 10 4. This implies that there is no major depletion of volatile carbon compared to xC measured in the natal cloud, hinting at a young disk. We also show that external FUV radiation impacts the outer disk and wind by vertically shifting the water freeze-out depth, which likely results in less e fficient grain growth and settling. This shift leads to nearly solar gas-phase C /O abundance ratios in these irradiated layers.