We investigated the ultrafast structural dynamics of cyclobutanone following photoexcitation at λ = 200 nm using gas-phase megaelectronvolt ultrafast electron diffraction. Our investigation complements the simulation studies of the same process within this special issue. It provides information about both electronic state population and structural dynamics through well-separable inelastic and elastic electron scattering signatures. We observe the depopulation of the photoexcited S2 state of cyclobutanone with n3s Rydberg character through its inelastic electron scattering signature with a time constant of (0.29 ± 0.2) ps toward the S1 state. The S1 state population undergoes ring-opening via a Norrish Type-I reaction, likely while passing through a conical intersection with S0. The corresponding structural changes can be tracked by elastic electron scattering signatures. These changes appear with a delay of (0.14 ± 0.05) ps with respect to the initial photoexcitation, which is less than the S2 depopulation time constant. This behavior provides evidence for the ballistic nature of the ring-opening once the S1 state is reached. The resulting biradical species react further within (1.2 ± 0.2) ps via two rival fragmentation channels yielding ketene and ethylene, or propene and carbon monoxide. Our study showcases the value of both gas-phase ultrafast diffraction studies as an experimental benchmark for nonadiabatic dynamics simulation methods and the limits in the interpretation of such experimental data without comparison with such simulations.

1.
Y.-C.
Cheng
and
G. R.
Fleming
, “
Dynamics of light harvesting in photosynthesis
,”
Annu. Rev. Phys. Chem.
60
,
241
262
(
2009
).
2.
D.
Polli
,
P.
Altoè
,
O.
Weingart
,
K. M.
Spillane
,
C.
Manzoni
,
D.
Brida
,
G.
Tomasello
,
G.
Orlandi
,
P.
Kukura
,
R. A.
Mathies
,
M.
Garavelli
, and
G.
Cerullo
, “
Conical intersection dynamics of the primary photoisomerization event in vision
,”
Nature
467
,
440
443
(
2010
).
3.
M. S.
Schuurman
and
A.
Stolow
, “
Dynamics at conical intersections
,”
Annu. Rev. Phys. Chem.
69
,
427
450
(
2018
).
4.
B. F. E.
Curchod
and
T. J.
Martínez
, “
Ab initio nonadiabatic quantum molecular dynamics
,”
Chem. Rev.
118
,
3305
3336
(
2018
).
5.
T. J. A.
Wolf
,
D. M.
Sanchez
,
J.
Yang
,
R. M.
Parrish
,
J. P. F.
Nunes
,
M.
Centurion
,
R.
Coffee
,
J. P.
Cryan
,
M.
Gühr
,
K.
Hegazy
,
A.
Kirrander
,
R. K.
Li
,
J.
Ruddock
,
X.
Shen
,
T.
Vecchione
,
S. P.
Weathersby
,
P. M.
Weber
,
K.
Wilkin
,
H.
Yong
,
Q.
Zheng
,
X. J.
Wang
,
M. P.
Minitti
, and
T. J.
Martínez
, “
The photochemical ring-opening of 1,3-cyclohexadiene imaged by ultrafast electron diffraction
,”
Nat. Chem.
11
,
504
509
(
2019
).
6.
E. G.
Champenois
,
D. M.
Sanchez
,
J.
Yang
,
J. P.
Figueira Nunes
,
A.
Attar
,
M.
Centurion
,
R.
Forbes
,
M.
Gühr
,
K.
Hegazy
,
F.
Ji
,
S. K.
Saha
,
Y.
Liu
,
M.-F.
Lin
,
D.
Luo
,
B.
Moore
,
X.
Shen
,
M. R.
Ware
,
X. J.
Wang
,
T. J.
Martínez
, and
T. J. A.
Wolf
, “
Conformer-specific photochemistry imaged in real space and time
,”
Science
374
,
178
182
(
2021
).
7.
Y.
Liu
,
D. M.
Sanchez
,
M. R.
Ware
,
E. G.
Champenois
,
J.
Yang
,
J. P. F.
Nunes
,
A.
Attar
,
M.
Centurion
,
J. P.
Cryan
,
R.
Forbes
,
K.
Hegazy
,
M. C.
Hoffmann
,
F.
Ji
,
M.-F.
Lin
,
D.
Luo
,
S. K.
Saha
,
X.
Shen
,
X. J.
Wang
,
T. J.
Martínez
, and
T. J. A.
Wolf
, “
Rehybridization dynamics into the pericyclic minimum of an electrocyclic reaction imaged in real-time
,”
Nat. Commun.
14
,
2795
(
2023
).
8.
Y.
Liu
,
R.
Xu
,
D. M.
Sanchez
,
T. J.
Martinez
, and
T. J. A.
Wolf
, “
Ultrafast events in electrocyclic ring-opening reactions
,”
Annu. Rev. Phys. Chem.
76
,
615
(
2025
).
9.
P.
Chakraborty
and
S.
Matsika
, “
Time-resolved photoelectron spectroscopy via trajectory surface hopping
,”
Wiley Interdiscip. Rev.: Comput. Mol. Sci.
14
,
e1715
(
2024
).
10.
J. P.
Figueira Nunes
,
L. M.
Ibele
,
S.
Pathak
,
A. R.
Attar
,
S.
Bhattacharyya
,
R.
Boll
,
K.
Borne
,
M.
Centurion
,
B.
Erk
,
M.-F.
Lin
,
R. J. G.
Forbes
,
N.
Goff
,
C. S.
Hansen
,
M.
Hoffmann
,
D. M. P.
Holland
,
R. A.
Ingle
,
D.
Luo
,
S. B.
Muvva
,
A. H.
Reid
,
A.
Rouzée
,
A.
Rudenko
,
S. K.
Saha
,
X.
Shen
,
A. S.
Venkatachalam
,
X.
Wang
,
M. R.
Ware
,
S. P.
Weathersby
,
K.
Wilkin
,
T. J. A.
Wolf
,
Y.
Xiong
,
J.
Yang
,
M. N. R.
Ashfold
,
D.
Rolles
, and
B. F. E.
Curchod
, “
Monitoring the evolution of relative product populations at early times during a photochemical reaction
,”
J. Am. Chem. Soc.
146
,
4134
(
2024
).
11.
S.
Pathak
,
L. M.
Ibele
,
R.
Boll
,
C.
Callegari
,
A.
Demidovich
,
B.
Erk
,
R.
Feifel
,
R.
Forbes
,
M.
Di Fraia
,
L.
Giannessi
,
C. S.
Hansen
,
D. M. P.
Holland
,
R. A.
Ingle
,
R.
Mason
,
O.
Plekan
,
K. C.
Prince
,
A.
Rouzée
,
R. J.
Squibb
,
J.
Tross
,
M. N. R.
Ashfold
,
B. F. E.
Curchod
, and
D.
Rolles
, “
Tracking the ultraviolet-induced photochemistry of thiophenone during and after ultrafast ring opening
,”
Nat. Chem.
12
,
795
800
(
2020
).
12.
K. D.
Borne
,
J. C.
Cooper
,
M. N. R.
Ashfold
,
J.
Bachmann
,
S.
Bhattacharyya
,
R.
Boll
,
M.
Bonanomi
,
M.
Bosch
,
C.
Callegari
,
M.
Centurion
,
M.
Coreno
,
B. F. E.
Curchod
,
M. B.
Danailov
,
A.
Demidovich
,
M.
Di Fraia
,
B.
Erk
,
D.
Faccialà
,
R.
Feifel
,
R. J. G.
Forbes
,
C. S.
Hansen
,
D. M. P.
Holland
,
R. A.
Ingle
,
R.
Lindh
,
L.
Ma
,
H. G.
McGhee
,
S. B.
Muvva
,
J. P. F.
Nunes
,
A.
Odate
,
S.
Pathak
,
O.
Plekan
,
K. C.
Prince
,
P.
Rebernik
,
A.
Rouzée
,
A.
Rudenko
,
A.
Simoncig
,
R. J.
Squibb
,
A. S.
Venkatachalam
,
C.
Vozzi
,
P. M.
Weber
,
A.
Kirrander
, and
D.
Rolles
, “
Ultrafast electronic relaxation pathways of the molecular photoswitch quadricyclane
,”
Nat. Chem.
16
,
499
505
(
2024
).
13.
B.
Stankus
,
H.
Yong
,
N.
Zotev
,
J. M.
Ruddock
,
D.
Bellshaw
,
T. J.
Lane
,
M.
Liang
,
S.
Boutet
,
S.
Carbajo
,
J. S.
Robinson
,
W.
Du
,
N.
Goff
,
Y.
Chang
,
J. E.
Koglin
,
M. P.
Minitti
,
A.
Kirrander
, and
P. M.
Weber
, “
Ultrafast X-ray scattering reveals vibrational coherence following Rydberg excitation
,”
Nat. Chem.
11
,
716
721
(
2019
).
14.
M. P.
Minitti
,
J. M.
Budarz
,
A.
Kirrander
,
J. S.
Robinson
,
D.
Ratner
,
T. J.
Lane
,
D.
Zhu
,
J. M.
Glownia
,
M.
Kozina
,
H. T.
Lemke
,
M.
Sikorski
,
Y.
Feng
,
S.
Nelson
,
K.
Saita
,
B.
Stankus
,
T.
Northey
,
J. B.
Hastings
, and
P. M.
Weber
, “
Imaging molecular motion: Femtosecond X-ray scattering of an electrocyclic chemical reaction
,”
Phys. Rev. Lett.
114
,
255501
(
2015
).
15.
Y.
Liu
,
S. L.
Horton
,
J.
Yang
,
J. P. F.
Nunes
,
X.
Shen
,
T. J. A.
Wolf
,
R.
Forbes
,
C.
Cheng
,
B.
Moore
,
M.
Centurion
,
K.
Hegazy
,
R.
Li
,
M.-F.
Lin
,
A.
Stolow
,
P.
Hockett
,
T.
Rozgonyi
,
P.
Marquetand
,
X.
Wang
, and
T.
Weinacht
, “
Spectroscopic and structural probing of excited-state molecular dynamics with time-resolved photoelectron spectroscopy and ultrafast electron diffraction
,”
Phys. Rev. X
10
,
021016
(
2020
).
16.
M. R.
Coates
,
M. A. B.
Larsen
,
R.
Forbes
,
S. P.
Neville
,
A. E.
Boguslavskiy
,
I.
Wilkinson
,
T. I.
Sølling
,
R.
Lausten
,
A.
Stolow
, and
M. S.
Schuurman
, “
Vacuum ultraviolet excited state dynamics of the smallest ring, cyclopropane. II. Time-resolved photoelectron spectroscopy and ab initio dynamics
,”
J. Chem. Phys.
149
,
144311
(
2018
).
17.
S. P.
Neville
,
Y.
Wang
,
A. E.
Boguslavskiy
,
A.
Stolow
, and
M. S.
Schuurman
, “
Substituent effects on dynamics at conical intersections: Allene and methyl allenes
,”
J. Chem. Phys.
144
,
014305
(
2016
).
18.
T. J. A.
Wolf
,
T. S.
Kuhlman
,
O.
Schalk
,
T. J.
Martínez
,
K. B.
Møller
,
A.
Stolow
, and
A.-N.
Unterreiner
, “
Hexamethylcyclopentadiene: Time-resolved photoelectron spectroscopy and ab initio multiple spawning simulations
,”
Phys. Chem. Chem. Phys.
16
,
11770
11779
(
2014
).
19.
J.
Yang
,
X.
Zhu
,
J. P. F.
Nunes
,
J. K.
Yu
,
R. M.
Parrish
,
T. J. A.
Wolf
,
M.
Centurion
,
M.
Gühr
,
R.
Li
,
Y.
Liu
,
B.
Moore
,
M.
Niebuhr
,
S.
Park
,
X.
Shen
,
S.
Weathersby
,
T.
Weinacht
,
T. J.
Martinez
, and
X.
Wang
, “
Simultaneous observation of nuclear and electronic dynamics by ultrafast electron diffraction
,”
Science
368
,
885
889
(
2020
).
20.
E. G.
Champenois
,
N. H.
List
,
M.
Ware
,
M.
Britton
,
P. H.
Bucksbaum
,
X.
Cheng
,
M.
Centurion
,
J. P.
Cryan
,
R.
Forbes
,
I.
Gabalski
,
K.
Hegazy
,
M. C.
Hoffmann
,
A. J.
Howard
,
F.
Ji
,
M.-F.
Lin
,
J. P. F.
Nunes
,
X.
Shen
,
J.
Yang
,
X.
Wang
,
T. J.
Martinez
, and
T. J.
Wolf
, “
Femtosecond electronic and hydrogen structural dynamics in ammonia imaged with ultrafast electron diffraction
,”
Phys. Rev. Lett.
131
,
143001
(
2023
).
21.
P.
Chakraborty
,
Y.
Liu
,
S.
McClung
,
T.
Weinacht
, and
S.
Matsika
, “
Nonadiabatic excited state dynamics of organic chromophores: Take-home messages
,”
J. Phys. Chem. A
126
,
6021
6031
(
2022
).
22.
P.
Chakraborty
,
Y.
Liu
,
S.
McClung
,
T.
Weinacht
, and
S.
Matsika
, “
Time resolved photoelectron spectroscopy as a test of electronic structure and nonadiabatic dynamics
,”
J. Phys. Chem. Lett.
12
,
5099
5104
(
2021
).
23.
H.
Yong
,
A.
Kirrander
, and
P. M.
Weber
, “
Time-resolved X-ray scattering of excited state structure and dynamics
,” in
Structural Dynamics with X-Ray and Electron Scattering
(
RSC Publishing
,
2023
).
24.
M.
Centurion
,
T. J. A.
Wolf
, and
J.
Yang
, “
Ultrafast imaging of molecules with electron diffraction
,”
Annu. Rev. Phys. Chem.
73
,
21
42
(
2022
).
25.
M.
Dunne
,
R. W.
Schoenlein
,
J. P.
Cryan
, and
T. J. A.
Wolf
, “
Free electron lasers for X-ray scattering and diffraction
,” in
Structural Dynamics with X-Ray and Electron Scattering
(
RSC Publishing
,
2023
).
26.
S. P.
Weathersby
,
G.
Brown
,
M.
Centurion
,
T. F.
Chase
,
R.
Coffee
,
J.
Corbett
,
J. P.
Eichner
,
J. C.
Frisch
,
A. R.
Fry
,
M.
Gühr
,
N.
Hartmann
,
C.
Hast
,
R.
Hettel
,
R. K.
Jobe
,
E. N.
Jongewaard
,
J. R.
Lewandowski
,
R. K.
Li
,
A. M.
Lindenberg
,
I.
Makasyuk
,
J. E.
May
,
D.
McCormick
,
M. N.
Nguyen
,
A. H.
Reid
,
X.
Shen
,
K.
Sokolowski-Tinten
,
T.
Vecchione
,
S. L.
Vetter
,
J.
Wu
,
J.
Yang
,
H. A.
Dürr
, and
X. J.
Wang
, “
Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory
,”
Rev. Sci. Instrum.
86
,
073702
(
2015
).
27.
H.
Yong
,
N.
Zotev
,
J. M.
Ruddock
,
B.
Stankus
,
M.
Simmermacher
,
A. M.
Carrascosa
,
W.
Du
,
N.
Goff
,
Y.
Chang
,
D.
Bellshaw
,
M.
Liang
,
S.
Carbajo
,
J. E.
Koglin
,
J. S.
Robinson
,
S.
Boutet
,
M. P.
Minitti
,
A.
Kirrander
, and
P. M.
Weber
, “
Observation of the molecular response to light upon photoexcitation
,”
Nat. Commun.
11
,
2157
(
2020
).
28.
R. M.
Parrish
and
T. J.
Martínez
, “
Ab initio computation of rotationally-averaged pump–probe X-ray and electron diffraction signals
,”
J. Chem. Theory Comput.
15
,
1523
1537
(
2019
).
29.
T.
Northey
,
N.
Zotev
, and
A.
Kirrander
, “
Ab initio calculation of molecular diffraction
,”
J. Chem. Theory Comput.
10
,
4911
4920
(
2014
).
30.
S.-H.
Xia
,
X.-Y.
Liu
,
Q.
Fang
, and
G.
Cui
, “
Excited-state ring-opening mechanism of cyclic ketones: A MS-CASPT2//CASSCF study
,”
J. Phys. Chem. A
119
,
3569
3576
(
2015
).
31.
S. W.
Benson
and
G. B.
Kistiakowsky
, “
The photochemical decomposition of cyclic ketones
,”
J. Am. Chem. Soc.
64
,
80
86
(
1942
).
32.
R. J.
Campbell
,
E. W.
Schlag
, and
B. W.
Ristow
, “
Mechanistic consequences of curved Stern-Volmer plots. Photolysis of cyclobutanone
,”
J. Am. Chem. Soc.
89
,
5098
5102
(
1967
).
33.
E. K. C.
Lee
, “
Laser photochemistry of selected vibronic and rotational states
,”
Acc. Chem. Res.
10
,
319
326
(
1977
).
34.
E. W.-G.
Diau
,
J. L.
Herek
,
Z. H.
Kim
, and
A. H.
Zewail
, “
Femtosecond activation of reactions and the concept of nonergodic molecules
,”
Science
279
,
847
851
(
1998
).
35.
E. W.-G.
Diau
,
C.
Kötting
, and
A. H.
Zewail
, “
Femtochemistry of Norrish type-I reactions: II. The anomalous predissociation dynamics of cyclobutanone on the S1 surface
,”
ChemPhysChem
2
,
294
309
(
2001
).
36.
M.-H.
Kao
,
R. K.
Venkatraman
,
M. N. R.
Ashfold
, and
A. J.
Orr-Ewing
, “
Effects of ring-strain on the ultrafast photochemistry of cyclic ketones
,”
Chem. Sci.
11
,
1991
2000
(
2020
).
37.
O.
Bennett
,
A.
Freibert
,
K. E.
Spinlove
, and
G. A.
Worth
, “
Prediction through quantum dynamics simulations: Photo-excited cyclobutanone
,”
J. Chem. Phys.
160
,
174305
(
2024
).
38.
J.
Eng
,
C. D.
Rankine
, and
T. J.
Penfold
, “
The photochemistry of Rydberg-excited cyclobutanone: Photoinduced processes and ground state dynamics
,”
J. Chem. Phys.
160
,
154301
(
2024
).
39.
D.
Hait
,
D.
Lahana
,
O. J.
Fajen
,
A. S. P.
Paz
,
P. A.
Unzueta
,
B.
Rana
,
L.
Lu
,
Y.
Wang
,
E. F.
Kjønstad
,
H.
Koch
, and
T. J.
Martínez
, “
Prediction of photodynamics of 200 nm excited cyclobutanone with linear response electronic structure and ab initio multiple spawning
,”
J. Chem. Phys.
160
,
244101
(
2024
).
40.
L.
Hutton
,
A.
Moreno Carrascosa
,
A. W.
Prentice
,
M.
Simmermacher
,
J. E.
Runeson
,
M. J.
Paterson
, and
A.
Kirrander
, “
Using a multistate mapping approach to surface hopping to predict the ultrafast electron diffraction signal of gas-phase cyclobutanone
,”
J. Chem. Phys.
160
,
204307
(
2024
).
41.
V. K.
Jaiswal
,
F.
Montorsi
,
F.
Aleotti
,
F.
Segatta
,
D.
Keefer
,
S.
Mukamel
,
A.
Nenov
,
I.
Conti
, and
M.
Garavelli
, “
Ultrafast photochemistry and electron-diffraction spectra in n → (3s) Rydberg excited cyclobutanone resolved at the multireference perturbative level
,”
J. Chem. Phys.
160
,
164316
(
2024
).
42.
J.
Janoš
,
J. P.
Figueira Nunes
,
D.
Hollas
,
P.
Slavíček
, and
B. F. E.
Curchod
, “
Predicting the photodynamics of cyclobutanone triggered by a laser pulse at 200 nm and its MeV-UED signals—A trajectory surface hopping and XMS-CASPT2 perspective
,”
J. Chem. Phys.
160
,
144305
(
2024
).
43.
J. E.
Lawrence
,
I. M.
Ansari
,
J. R.
Mannouch
,
M. A.
Manae
,
K.
Asnaashari
,
A.
Kelly
, and
J. O.
Richardson
, “
A MASH simulation of the photoexcited dynamics of cyclobutanone
,”
J. Chem. Phys.
160
,
174306
(
2024
).
44.
D. V.
Makhov
,
L.
Hutton
,
A.
Kirrander
, and
D. V.
Shalashilin
, “
Ultrafast electron diffraction of photoexcited gas-phase cyclobutanone predicted by ab initio multiple cloning simulations
,”
J. Chem. Phys.
160
,
164310
(
2024
).
45.
A.
Martín Santa Daría
,
J.
Hernández-Rodríguez
,
L. M.
Ibele
, and
S.
Gómez
, “
Photofragmentation of cyclobutanone at 200 nm: TDDFT vs CASSCF electron diffraction
,”
J. Chem. Phys.
160
,
114303
(
2024
).
46.
X.
Miao
,
K.
Diemer
, and
R.
Mitrić
, “
A CASSCF/MRCI trajectory surface hopping simulation of the photochemical dynamics and the gas phase ultrafast electron diffraction patterns of cyclobutanone
,”
J. Chem. Phys.
160
,
124309
(
2024
).
47.
J.
Suchan
,
F.
Liang
,
A. S.
Durden
, and
B. G.
Levine
, “
Prediction challenge: First principles simulation of the ultrafast electron diffraction spectrum of cyclobutanone
,”
J. Chem. Phys.
160
,
134310
(
2024
).
48.
E. R.
Miller
,
S. J.
Hoehn
,
A.
Kumar
,
D.
Jiang
, and
S. M.
Parker
, “
Ultrafast photochemistry and electron diffraction for cyclobutanone in the S2 state: Surface hopping with time-dependent density functional theory
,”
J. Chem. Phys.
161
,
034105
(
2024
).
49.
S.
Mukherjee
,
R. S.
Mattos
,
J. M.
Toldo
,
H.
Lischka
, and
M.
Barbatti
, “
Prediction Challenge: Simulating Rydberg photoexcited cyclobutanone with surface hopping dynamics based on different electronic structure methods
,”
J. Chem. Phys.
160
,
154306
(
2024
).
50.
J.
Peng
,
H.
Liu
, and
Z.
Lan
, “
The photodissociation dynamics and ultrafast electron diffraction image of cyclobutanone from the surface hopping dynamics simulation
,”
J. Chem. Phys.
160
,
224305
(
2024
).
51.
P.
Vindel-Zandbergen
and
J.
González-Vázquez
, “
Non-adiabatic dynamics of photoexcited cyclobutanone: Predicting structural measurements from trajectory surface hopping with XMS-CASPT2 simulations
,”
J. Chem. Phys.
161
,
024104
(
2024
).
52.
H.
Akimoto
,
Atmospheric Reaction Chemistry
(
Springer
,
Berlin, Heidelberg
,
2016
).
53.
M. L.
Hause
,
N.
Herath
,
R.
Zhu
,
M. C.
Lin
, and
A. G.
Suits
, “
Roaming-mediated isomerization in the photodissociation of nitrobenzene
,”
Nat. Chem.
3
,
932
937
(
2011
).
54.
T.
Endo
,
S. P.
Neville
,
V.
Wanie
,
S.
Beaulieu
,
C.
Qu
,
J.
Deschamps
,
P.
Lassonde
,
B. E.
Schmidt
,
H.
Fujise
,
M.
Fushitani
,
A.
Hishikawa
,
P. L.
Houston
,
J. M.
Bowman
,
M. S.
Schuurman
,
F.
Légaré
, and
H.
Ibrahim
, “
Capturing roaming molecular fragments in real time
,”
Science
370
,
1072
1077
(
2020
).
55.
L.
O’Toole
,
P.
Brint
,
C.
Kosmidis
,
G.
Boulakis
, and
P.
Tsekeris
, “
Vacuum-ultraviolet absorption spectra of propanone, butanone and the cyclic ketones CnH2n−2O (n = 4, 5, 6, 7)
,”
J. Chem. Soc., Faraday Trans.
87
,
3343
3351
(
1991
).
56.
T. S.
Kuhlman
,
S. P. A.
Sauer
,
T. I.
Sølling
, and
K. B.
Møller
, “
Symmetry, vibrational energy redistribution and vibronic coupling: The internal conversion processes of cycloketones
,”
J. Chem. Phys.
137
,
22A522
(
2012
).
57.
K.
Tamagawa
and
R. L.
Hilderbrandt
, “
Molecular structure of cyclobutanone as determined by combined analysis of electron diffraction and spectroscopic data
,”
J. Phys. Chem.
87
,
5508
5516
(
1983
).
58.
W. M.
Stigliani
,
V. W.
Laurie
, and
L. H.
Scharpen
, “
Structure of cyclobutanone
,”
J. Mol. Spectrosc.
62
,
85
89
(
1976
).
59.
J. C.
Hemminger
and
E. K. C.
Lee
, “
Fluorescence excitation and photodecomposition of the first excited singlet cyclobutanone (1A2): A study of predissociation of and collisional energy transfer from the vibronically selected species
,”
J. Chem. Phys.
56
,
5284
5295
(
1972
).
60.
S.
Pedersen
,
J. L.
Herek
, and
A. H.
Zewail
, “
The validity of the ‘diradical’ hypothesis: Direct femtoscond studies of the transition-state structures
,”
Science
266
,
1359
1364
(
1994
).
61.
M.
Koch
,
T. J. A.
Wolf
, and
M.
Gühr
, “
Understanding the modulation mechanism in resonance-enhanced multiphoton probing of molecular dynamics
,”
Phys. Rev. A
91
,
031403(R)
(
2015
).
62.
K. A.
Trentelman
,
D. B.
Moss
,
S. H.
Kable
, and
P. L.
Houston
, “
The 193-nm photodissociation of cyclobutanone: Dynamics of the C2 and C3 channels
,”
J. Phys. Chem.
94
,
3031
3039
(
1990
).
63.
M.
Kasha
, “
Characterization of electronic transitions in complex molecules
,”
Discuss. Faraday Soc.
9
,
14
19
(
1950
).
64.
T. S.
Kuhlman
,
T. I.
Sølling
, and
K. B.
Møller
, “
Coherent motion reveals non-ergodic nature of internal conversion between excited states
,”
ChemPhysChem
13
,
820
827
(
2012
).
65.
T. S.
Kuhlman
,
M.
Pittelkow
,
T. I.
Sølling
, and
K. B.
Møller
, “
Pulling the levers of photophysics: How structure controls the rate of energy dissipation
,”
Angew. Chem., Int. Ed.
52
,
2247
2250
(
2013
).
66.
M.-F.
Lin
,
A. H.
Reid
,
X.
Shen
, and
T. J. A.
Wolf
, “
Imaging ultrafast structural dynamics with megaelectronvolt ultrafast electron diffraction
,” in
Structural Dynamics with X-Ray and Electron Scattering
(
RSC Publishing
,
2023
).
67.
X.
Shen
,
J. P. F.
Nunes
,
J.
Yang
,
R. K.
Jobe
,
R. K.
Li
,
M.-F.
Lin
,
B.
Moore
,
M.
Niebuhr
,
S. P.
Weathersby
,
T. J. A.
Wolf
,
C.
Yoneda
,
M.
Guehr
,
M.
Centurion
, and
X. J.
Wang
, “
Femtosecond gas-phase mega-electron-volt ultrafast electron diffraction
,”
Struct. Dyn.
6
,
054305
(
2019
).
68.
F.
Neese
, “
Software update: The ORCA program system—Version 5.0
,”
Wiley Interdiscip. Rev.: Comput. Mol. Sci.
12
,
e1606
(
2022
).
69.
F.
Neese
,
F.
Wennmohs
,
A.
Hansen
, and
U.
Becker
, “
Efficient, approximate and parallel Hartree–Fock and hybrid DFT calculations. A ‘chain-of-spheres’ algorithm for the Hartree–Fock exchange
,”
Chem. Phys.
356
,
98
109
(
2009
).
70.
B.
Helmich-Paris
,
B.
de Souza
,
F.
Neese
, and
R.
Izsák
, “
An improved chain of spheres for exchange algorithm
,”
J. Chem. Phys.
155
,
104109
(
2021
).
71.
F.
Neese
, “
The SHARK integral generation and digestion system
,”
J. Comput. Chem.
44
,
381
396
(
2023
).
72.
T. J. A.
Wolf
(
2020
). “
Diffraction simulation
,” GitHub. https://github.com/thomasjawolf/diffraction_simulation
73.
F.
Salvat
,
A.
Jablonski
, and
C. J.
Powell
, “
ELSEPA—Dirac partial-wave calculation of elastic scattering of electrons and positrons by atoms, positive ions and molecules
,”
Comput. Phys. Commun.
165
,
157
190
(
2005
).
74.
L. S.
Bartell
and
R. M.
Gavin
, “
Effects of electron correlation in X-ray and electron diffraction
,”
J. Am. Chem. Soc.
86
,
3493
3498
(
1964
).
75.
J. P. F.
Nunes
,
M.
Williams
,
J.
Yang
,
T. J. A.
Wolf
,
C. D.
Rankine
,
R.
Parrish
,
B.
Moore
,
K.
Wilkin
,
X.
Shen
,
M.-F.
Lin
,
K.
Hegazy
,
R.
Li
,
S.
Weathersby
,
T. J.
Martinez
,
X. J.
Wang
, and
M.
Centurion
, “
Photo-induced structural dynamics of o-nitrophenol by ultrafast electron diffraction
,”
Phys. Chem. Chem. Phys.
26
,
17991
17998
(
2024
).
76.
A. L.
Bennani
,
A.
Duguet
, and
H. F.
Wellenstein
, “
Differential cross sections for 35 keV electrons elastically scattered from NH3
,”
J. Phys. B
12
,
461
472
(
1979
).
77.
I.
Hargittai
and
M.
Hargittai
,
Stereochemical Applications of Gas-Phase Electron Diffraction, Part A
(
John Wiley & Sons
,
1988
).
78.
A.
Duguet
,
A.
Lahmam-Bennani
, and
M.
Rouault
, “
High energy elastic and inelastic electron scattering by the NH3 molecule-binding effect
,”
J. Chem. Phys.
78
,
6595
6597
(
1983
).
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