Domain 2 of 10
Excited States and Spectroscopy
Excited states from CIS to EOM-CCSD, and the spectra a lab measures: UV-Vis, ECD, IR, Raman, VCD, ROA, NMR, EPR and core X-ray.
7 Checked16 Partial3 UnverifiedEngine 1.10.12 live
Walkthrough
Seven Spectra, One Suite
Step through the spectra the engine computes. The caffeine IR is real engine output; the other shapes are schematic.
Space or K plays and pauses, the arrow keys step. With reduced motion every step is shown at once.
Spectroscopy suiteIR real, others schematic shapes
IRRamanROAVCDUV-Vis and ECDNMREPR
Real engine output
SupportChecked
FromWilson, Decius, Cross 1955
1. IR Harmonic frequencies and intensities. Real engine output for caffeine.
What You Can Compute
UV-Vis and ECD
CIS, TDA and TDDFT singlets and triplets with oscillator and rotatory strengths, broadened spectra.
Correlated Excitations
EOM-CCSD checked against Stanton and Bartlett 1993; RI-CC2, SCS-CC2 and SOS-CC2 for closed shells, with SCS-CC2 S1-T1 gaps of three MR-TADF emitters matching Hall 2022 (0.21, 0.27, 0.16 eV); ADC(2), EOM-IP, EOM-EA, exact CC2 and spin-flip TDA are built, with no printed check for them yet.
Vibrational Spectra
IR, Raman, VPT2 anharmonic fundamentals and intensities, vibronic spectra, VCD and ROA.
Magnetic Resonance
GIAO NMR shielding, spin-spin couplings, EPR hyperfine tensors and the g-tensor.
Core Spectra
X-ray absorption by Delta-SCF and core-valence separation for K edges of Li to Ne, and the transition-potential method for Na to Ar as well. Closed-shell references.
Excited-State Dynamics
Excited-state gradients for emission and fewest-switches surface hopping on CIS or TDA states.
Excited-State Analysis
Natural transition orbitals, difference and attached or detached densities, real-time TDDFT, conical intersections and crossing points, and radiative and intersystem crossing rates.
Every Method, with Its Level of Support
Generated from the engine's own capability report (engine 1.10.12), so this list never runs ahead of the code.
Checked reproduces printed values Checked (exact) no printed value exists; checked against exact mathematics or brute force Partial code exists, unchecked parts badged in the app Unverified built, no printed check yet
| Method | Support | Since | Primary Sources |
|---|---|---|---|
| Molecular GW and BSEG0W0 and evGW quasiparticle energies, ionisation potentials, electron affinities and gaps, and Bethe-Salpeter singlet and triplet excitations with oscillator strengths on an RHF or RKS reference. Molecules only and closed shell; no periodic GW or BSE and no dynamical BSE kernel. G0W0@PBE ionisation potentials reproduce van Setten et al. 2015 Table 2 (He, Ne). | Checked | 1.9.0 | Hedin 1965; van Setten et al. 2015 |
| Real-time TDDFTReal-time TDHF and TDDFT propagation with a second-order Magnus propagator and predictor-corrector, delta-kick absorption (dipole strength and the TRK sum), dipole time series and an optional continuous field. Closed-shell molecules; LDA, GGA and global hybrids only. Open-shell, range-separated, meta-GGA and VV10 functionals are refused. Selftest identities passed in the 1.9.0 gate; no printed spectrum reproduced yet. | Unverified | 1.9.0 | |
| Radiative, intersystem and reverse intersystem crossing ratesFluorescence and phosphorescence radiative rates and lifetimes in the Condon limit with a triplet sublevel Boltzmann average, and golden-rule intersystem crossing and reverse intersystem crossing rates with El-Sayed classification, from spin-orbit couplings. Marcus-Levich-Jortner high-temperature form only; no spin-orbit quasi-degenerate phosphorescence dipoles; spin-orbit couplings have no solvent. Radiative rates reproduce Strickler and Berg 1962 Table I (11 lifetimes, largest relative difference 0.07%); intersystem crossing rates are checked at formula level only (Englman and Jortner 1970). | Partial | 1.9.0 | de Souza et al. 2019; Marian 2012; Strickler, Berg 1962; Englman, Jortner 1970 |
| Conical intersections, MECP and derivative couplingsMinimum-energy crossing points between states of different spin (MECP) and conical intersection points of the same spin (MECI) by a projected mean-energy gradient with a constraint step, derivative coupling vectors between singlet TDA and CIS states by finite differences, and numerical gradients of EOM-CCSD, ADC(2) and CC2 states. Crossings up to 30 atoms, couplings up to 20 atoms, correlated-state gradients up to 8 atoms. States from an SCF ground state or TDA/TDDFT roots with LDA, GGA, global hybrids or Hartree-Fock. Couplings and gradients are numerical, not analytic. No printed crossing geometry reproduced yet. | Unverified | 1.9.0 | Jensen 2017; Hammes-Schiffer, Tully 1994 |
| CIS, TDA and TDDFTSinglet and triplet excitations, oscillator strengths, UV-Vis and ECD spectra. Printed-value check covers CIS excitation energies only (Foresman et al. 1992 Table I: formaldehyde, 32 energies in the STO-3G, 6-31G and 6-31G* columns). TDA and TDDFT energies, oscillator strengths and ECD are checked by exact identities and independent routes (explicit matrices, the polarisability sum rule, size consistency), not against printed values. | Checked | 0.7.65 | Foresman et al. 1992; Hirata, Head-Gordon 1999; Casida 1995 |
| Natural transition orbitals and difference densitiesNatural transition orbital pairs with hole and particle orbitals, unrelaxed difference density, attached and detached electron densities and the unrelaxed excited-state dipole moment, for CIS, TDA, TDHF, TDDFT and spin-flip TDA states. Unrelaxed densities only; not offered for EOM-CCSD, CC2 or ADC(2) states. No printed orbital analysis reproduced yet. | Partial | 1.5.0 | |
| EOM-CCSDCorrelated excitation energies and strengths on RHF references; CH+ reproduced from Stanton and Bartlett 1993. | Checked | 0.9.0 | Stanton, Bartlett 1993 |
| ADC(2)Second-order algebraic diagrammatic construction excitation energies and strengths on RHF references. Checked by exact-property tests only; no printed excitation energy reproduced yet. | Unverified | 0.9.0 | Schirmer 1982 |
| RI-CC2, SCS-CC2 and SOS-CC2Singlet and triplet vertical excitations on a closed-shell Hartree-Fock reference, with doubles never stored. Closed-shell RHF only; no transition moments, gradients or solvent; SOS-CC2 has no printed check. | Partial | 1.10.0 | Hattig, Weigend 2000; Hellweg, Grun, Hattig 2008 |
| Excited states in solventCIS, TDA, TDHF and TDDFT energies and gradients in IEF-PCM or COSMO, equilibrium linear response. No nonequilibrium or state-specific schemes. | Partial | 1.10.0 | Tomasi, Mennucci, Cammi 2005 |
| Correlation function rates (TVCF)Golden-rule internal conversion and intersystem crossing between two harmonic states with Duschinsky rotation, plus the spin-orbit coupling derivative. Checked at formula level against Englman and Jortner 1970 and against sum over states; no published rate reproduced yet. | Partial | 1.10.0 | Peng et al. 2007; Niu et al. 2010; Peng et al. 2013; Englman, Jortner 1970 |
| Nonadiabatic couplings (Send-Furche)Ground to excited state derivative couplings from TDHF, TDDFT or TDA linear response, closed and open shell; guided form in Engine tools. Coupling to the ground state only. Printed-value check: the hydrogen-atom TDHF coupling against the exact value in Send, Furche 2010 Table III. Kohn-Sham couplings (PBE, PBE0) are checked against numerical orbital response only; no printed Kohn-Sham value is reproduced yet (the printed PBE0 hydrogen value needs the 10s8p basis from the paper's supplementary material, which is not held). | Partial | 1.10.1 | Send, Furche 2010 |
| Excited-state gradientsCIS, TDA and TDDFT gradients for excited-state optimisation and emission. | Partial | 0.7.53 | Furche, Ahlrichs 2002 |
| Core spectra (Delta-SCF, CVS)X-ray absorption by Delta-SCF and core-valence separation for K edges of Li to Ne, and the transition-potential method (half core hole, built in 1.8.0) that also reaches Na to Ar. Built, not tested numerically against a published table. Closed-shell references only. K edges only; L edges are not built. Nonrelativistic: no scalar-relativistic shift. | Partial | 0.7.52 | Cederbaum, Domcke, Schirmer 1980; Besley, Gilbert, Gill 2009; Triguero, Pettersson, Agren 1998 |
| IR spectraHarmonic frequencies and intensities, scaled columns, broadened spectra. | Checked | 0.6 | Wilson, Decius, Cross 1955 |
| Raman intensitiesRaman activities from polarisability derivatives. Hartree-Fock. | Partial | 0.7.65 | Porezag, Pederson 1996 |
| VPT2 anharmonic frequenciesAnharmonic constants and fundamentals with variational Fermi resonance treatment. No states of three or more quanta. | Checked | 1.2.0 | Barone 2005; Martin et al. 1995; Clabo et al. 1988 |
| NMR shielding (GIAO)Shielding tensors and chemical shifts for HF, LDA, GGA and global hybrids. Printed-value check is GIAO Hartree-Fock only (Wolinski, Hinton, Pulay 1990 Tables I and V: methane and benzene, with the geometry set by the printed SCF energy because the paper prints none). DFT shieldings are checked against finite-field Kohn-Sham calculations and the published functional ordering, not against printed numbers. | Checked | 0.7.65 | Wolinski, Hinton, Pulay 1990 |
| NMR spin-spin couplingsFermi contact, spin-dipole, PSO and DSO terms. Fermi contact and spin-dipole terms are checked against finite-field calculations, all terms by exact symmetry identities, and the nuclear g factors against Stone 2005 Table 1. No printed coupling constant is reproduced yet. | Partial | 1.0.0 | Ramsey 1953; Helgaker et al. 2000 |
| EPR hyperfine and g-tensorHyperfine tensors and the g-tensor for UHF and UKS. Hyperfine printed-value check is UHF only (methyl radical, Szabo and Ostlund 1996 Table 3.26); UKS hyperfine couplings are checked by identities only. Two hydrogen-atom comparisons with the measured 1420 MHz hyperfine frequency stay pending: the source of that value is not held. The g-tensor check is listed under EPR g-tensor in Relativistic and Magnetic. | Checked | 0.7.54 | Neese 2001; Szabo, Ostlund 1996 |
| VCD spectraRotational strengths with GIAO atomic axial tensors, analytic for RHF and RKS. | Partial | 1.0.0 | Stephens 1985; Cheeseman et al. 1996 |
| Raman optical activityStatic-limit ROA invariants with coupled Hartree-Fock. Frequency-dependent and Kohn-Sham ROA are not offered. | Partial | 1.2.0 | Polavarapu 1990 |
| Surface hopping (FSSH)Fewest-switches surface hopping on CIS or TDA singlets and model problems. No hops into S0, no decoherence correction. | Partial | 1.2.0 | Tully 1990; Hammes-Schiffer, Tully 1994 |
| Spin-flip TDA, EOM-IP/EA-CCSD and CC2Spin-flip excitations from high-spin references, ionisation energies, electron affinities and CC2 excitations. No CC2 strengths or meta-GGA TDDFT kernel. RI-CC2 is its own row. | Partial | 1.5.0 | Shao, Head-Gordon, Krylov 2003; Christiansen, Koch, Jorgensen 1995 |
| Vibronic spectra and anharmonic intensitiesVibrationally resolved absorption and emission spectra with Franck-Condon and Herzberg-Teller moments, Duschinsky rotation, adiabatic Hessian, vertical Hessian and vertical gradient models, time-independent and time-dependent (0 K) methods, Boltzmann initial states, resonance Raman A term, and VPT2 IR and Raman intensities. 3 to 200 atoms (3 to 40 when the initial state comes from a job). Variational GVPT2 intensities not built. Matches the closed Franck-Condon formulas of Sharp and Rosenstock 1964 to 1e-13; the paper prints figures only, so no printed spectrum is reproduced. | Partial | 1.5.0 | Santoro et al. 2007; Bloino, Barone 2012; Sharp, Rosenstock 1964 |
| DFT Raman and finite-field hyperpolarizabilityRaman intensities from a Kohn-Sham Hessian and finite-field polarizabilities, and the first hyperpolarizability by finite field with Richardson extrapolation. Built, not tested numerically. Meta-GGA, VV10, range-separated and double hybrids refused; at most 20 atoms. | Partial | 1.7.0 | Porezag, Pederson 1996 |
Printed Value, Our Value
| Quantity | Source | Printed | Ours | Result |
|---|---|---|---|---|
| CH+ EOM-CCSD Excitation, eV | Stanton, Bartlett 1993 Table III | 3.261, 9.109, 13.580 | within 0.002 eV | Match |
| Water VPT2 Fundamentals, SCF/DZP | Clabo et al. 1988 | printed constants | reproduced | Match |
| H2O2 ROA Invariant 10^4 Dz | Polavarapu 1990 Table VI | -12 | -11.4 | Pattern |
| DOBNA, DiKTa, DABNA-1 S1-T1 Gap at SCS-CC2/cc-pVDZ, eV | Hall et al. 2022 | 0.21, 0.27, 0.16 | 0.210, 0.269, 0.159 | Match |
| HF and CO at HF/6-31G(d): Frequency, IR Intensity, Bond Length and Dipole | Yamaguchi et al. 1986 Table II, III | HF 4358 cm-1, 3.348 D2/(amu A2); CO 2439, 3.264 | HF 4357.9, 3.348; CO 2439.0, 3.264 | Match |
| G0W0@PBE/def2-QZVP Ionisation Potentials, He and Ne, eV | van Setten et al. 2015 Table 2, doi 10.1021/acs.jctc.5b00453 | 23.48, 20.38 | 23.477, 20.376 | Match |
| Strickler-Berg Radiative Lifetimes, 11 Molecules (E.g. Perylene), Ns | Strickler, Berg 1962 Table I, doi 10.1063/1.1733166 | 4.29 | 4.287 (largest relative difference 0.07%) | Match |
| Formaldehyde CIS Vertical Excitation Energies, STO-3G, 6-31G and 6-31G*, eV | Foresman et al. 1992 Table I, doi 10.1021/j100180a030 | 32 energies, 3 decimals | all 32 within 0.002 eV (largest difference 0.0019) | Match |
| Methane GIAO-RHF/6-31G Isotropic Shieldings of 13C and 1H | Wolinski, Hinton, Pulay 1990 Table I, doi 10.1021/ja00179a005 | 13C 207.36, 1H 32.93 ppm | 207.36, 32.93 ppm (r(CH) 1.086 A, set by the printed SCF energy; the paper prints no geometry) | Match |
| Methyl Radical UHF/STO-3G Spin Densities at C and H and Couplings a(13C), a(1H) | Szabo, Ostlund 1996 Table 3.26 p. 218, ISBN 978-0-486-69186-2 | 0.2480, -0.0340 a.u.; 99.3 G, -54.2 G | within 1e-4 a.u.; within 0.5 G (r(CH) 1.079 A, set by the printed spin densities; the page prints no geometry) | Match |
Not Offered Today
- Nonequilibrium and state-specific solvated excited states; solvent with the CC2 family
- Published correlation function (TVCF) rates reproduced: none yet, so rates are estimates
- Surface hopping into the ground state and decoherence corrections
- Frequency-dependent and Kohn-Sham ROA
- VPT2 states of three or more quanta
- g-tensor with meta-GGA or range-separated hybrids
- Analytic couplings between two excited states (ground-state couplings are analytic) and analytic EOM-CCSD, CC2 or ADC(2) gradients (finite differences only, small molecules)
- Real-time TDDFT for open shells, range-separated hybrids and meta-GGAs
In the Chemistry Lab
Start, then the Spectra task card. Pick UV-Vis, IR, Raman, NMR, EPR, VCD or ROA; the preset fills method and basis, and the Advanced tabs hold the rest.
Excited States and Spectroscopy Questions
Can I compare a computed IR spectrum with experiment?
Yes. Harmonic frequencies come with scaled columns and broadened spectra, and VPT2 gives anharmonic fundamentals for small molecules. The method gap is named beside the number.
Which excited-state method should I start with?
TDDFT with a range-separated hybrid for most organic molecules; EOM-CCSD for small molecules when you need a correlated reference. The preset explains its choice.
Are NMR shifts referenced?
Shielding tensors are computed with GIAO; shifts are given against a reference you pick, computed at the same level.
What can I learn about a UV-Vis band beyond its energy?
Natural transition orbitals show the hole and particle orbitals of a state, and difference, attached and detached densities show where charge moves. Both are computed from CIS, TDA, TDDFT or spin-flip states and are unrelaxed.
Can I find conical intersections and crossing points?
Yes, as built tools: minimum-energy crossing points (different spin) and conical intersection points (same spin) up to 30 atoms, with derivative couplings by finite differences. They are marked Unverified until a printed crossing geometry is reproduced.
Are vibronic spectra and intersystem crossing rates available?
Yes, both are marked Partial. Vibronic spectra (Franck-Condon and Herzberg-Teller, with Duschinsky rotation) match the closed Franck-Condon formulas of Sharp and Rosenstock 1964; that paper prints figures only, so no printed spectrum is reproduced. Radiative rates reproduce Strickler and Berg 1962 Table I; golden-rule intersystem crossing rates are checked at formula level only, and no published rate is reproduced yet.
See It on a Molecule of Your Own
See your own molecule optimised, its spectrum computed and the printed reference values shown beside the result.