andrade_2025

J. R. C. Andrade, M. Kretschmar, R. Danylo, S. Carlström, T. Witting, A. Mermillod-Blondin, S. Patchkovskii, M. Yu. Ivanov, M. J. J. Vrakking, A. Rouzée and T. Nagy, “Temporal characterization of tunable few-cycle vacuum ultraviolet pulses”, Nat. Photon. 19, 1240 (2025)

Source record · Catalogue · Review register

DOI: 10.1038/s41566-025-01770-6

Source kind: measurement

Recorded technique: Electron frequency-resolved optical gating (eFROG): few-femtosecond VUV pulses (resonant dispersive waves from a helium-filled capillary, tuned 160-190 nm, microjoules) split into two delayed replicas by D-shaped mirrors and focused into a xenon (or krypton) gas jet at 2-5e-5 mbar in a velocity-map-imaging spectrometer; the photoelectron spectrum of non-resonant two-photon ionisation recorded against delay, and the pulse retrieved by differential evolution with a two-channel (2P3/2, 2P1/2) incoherent-sum model and a delay-independent response function. Validated against TD-CIS calculations (Methods) and Luna propagation simulations.

Materials in structured entries: None recorded.

Dataset quantities: None recorded.

Contents: 0 datasets; 0 formulas.

Curation notes

Pages are PDF pages: pp. 1-7 are journal pp. 1240-1246; Methods (pp. 8-10) and Extended Data (pp. 11-12) are unnumbered. Identity checked against the first page (Nature Photonics 19, November 2025, 1240-1246). No supplementary information in the library.

NOTHING TAKEN. Two-photon ionisation enters only through the measured traces and a fitted, delay-independent response function mu(E) (Methods, ‘Phase retrieval’): ‘necessary to correctly include the spectral sensitivity of the apparatus and the frequency dependence of the two-photon ionization process including the contributions of the AIS’; the ratio C of the two spin-orbit channels’ yields is a retrieved parameter. No two-photon cross section, absolute or relative, is printed, and the figures (traces, spectra, pulse shapes) hold none. FROG errors 2.5 % and 2.1 % on the 74 x 132 grid for the 180 nm and 170 nm traces (p. 5).

EXTENDED DATA TABLE 1 (p. 11, tbl_a8d8c799f4ca, checked against the image), ‘Gases for non-sequential two-photon ionization by VUV pulses’: 1/2 Ip (eV), the lowest Rydberg state (eV) and the wavelength range (nm) between them, He-Xe. Not taken: rounded, derived values with no source named. Against nist_asd_2026 (computed 2026-10-08, CODATA hc/e): half of ie_<gas>_I is 12.2937 (He; printed 12.30), 10.7823 (10.78), 7.8798 (7.88), 6.9998 (7.00) and 6.0649 eV (Xe; printed 6.07, the half of 12.13 rounded up). The ‘lowest Rydberg state’ of Ne-Xe is the lowest odd-parity J = 1 level, the first resonance line: level_<gas>_odd_J1 is 16.6708, 11.6236, 10.0324 and 8.4365 eV (printed 16.67, 11.62, 10.03, 8.44). For He the printed 19.82 eV is the spin-forbidden 1s.2s 3S1 level (159855.97 cm^-1 = 19.8196 eV, NIST He_I_levels.tsv), not the 1s.2p 1P1 resonance (level_He_1s2p_1P1, 21.2180 eV) nor the two-photon 1s.2s 1S0 level (level_He_1s2s_1S0, 20.6158 eV). The wavelength ranges are hc over the two energies (He’s 62 nm is 62.56 truncated; the others are rounded). The table’s condition (2) excludes one-photon excitation; even-parity (two-photon) resonances are not considered.

EXTENDED DATA TABLE 2 (p. 12, tbl_f4d525d152a7, checked against the image): the TD-CIS (relativistic small-core ECP) ionisation potentials of Xe 5p3/2, 5p1/2 and 5s1/2, 12.026, 13.483 and 27.927 eV, against ‘Experiment’ (Saloman 2004, Hansen and Persson 1987) 12.130, 13.436, 23.397 eV, Delta -0.104, 0.047, 4.530 eV and ‘Rel. Delta’ -0.9, 0.3, 19.4 (printed ‘(eV)’; the values are per cent: -0.104/12.130 = -0.86 %). Not taken: the theory column is the model’s (a property of the calculation), the experiment column is reproduced. The experiment column agrees with NIST to the printed digits: ie_Xe_I 12.1298437 eV; plus level_Xe+_2P12 (10537.01 cm^-1) 13.43627 eV; plus the Xe II 5s.5p6 2S1/2 level (90873.83 cm^-1, NIST Xe_II_levels.tsv, row 3, not a dataset) 23.39676 eV. The text says the ECP ‘yields correct spin-orbit splitting albeit an ionization potential that is slightly too low’ (p. 8); the table’s TD-CIS splitting is 1.457 eV against the experimental 1.306 eV.

TD-CIS (Methods, pp. 8-9; Carlström et al., Phys. Rev. A 106, 043104 and 042806 (2022)): single excitations from the Hartree-Fock ground state, only from ns2 np6; Peterson et al.’s small-core relativistic ECP (J. Chem. Phys. 119, 11113 (2003)); radial grid to 300 bohr, r_j = r_(j-1) + rho_min + (1 - exp(-alpha r_(j-1))) (rho_max - rho_min) with rho_min = 0.12, rho_max = 0.17 bohr, alpha = 0.3; spinor spherical harmonics with l <= 10 and, for linear polarisation, Delta m_j = 0: 164 spin-angular partial waves; Manolopoulos complex absorbing potential over the last 231.77 bohr, delta = 0.20866; 10 time steps per atomic unit (about 413 per fs), the retrieved field interpolated by cubic Hermite splines and the vector potential integrated in the Fourier domain; photoelectron spectra by the surface-flux (iSURF) method; delays -5 to 5 fs, a background from a 20 fs delay subtracted, averaged over four CEP shifts of the delayed replica. The calculations validate the retrieval (Fig. 3); no ionisation yield or cross section from them is printed.

FURTHER TWO-PHOTON DATA CITED: none with values. Ref. 10 (F. Reiter et al., Opt. Lett. 35, 2248 (2010)) and Ref. 27 (T. Sekikawa, T. Katsura, S. Miura and S. Watanabe, Phys. Rev. Lett. 88, 193902 (2002)) use photoionisation for pulse measurement, not cross sections. The data repository (figshare, 10.6084/m9.figshare.29835218) holds the figures’ data, not in the library.

Recorded bibliographic identity status: VALIDATED. This concerns identification of the source; it does not establish the scientific correctness of its contents.

Datasets

No datasets are recorded.

Formulas

No formulas are recorded.

Corrections

No dataset errata are recorded in this source record.

Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the review register for the checks and decisions.