Seminars

Seminars will continue to be
held in room S141 on Mondays at 4:00PM
inperson and over Zoom, unless
noted otherwise. Check your
email for login instructions!


Spring 2022

February 14, 2022 (9AM, Zoom)

Dr.
Bharath
Hebbe
Madhusudhana,
LMU
Munich

Quantum simulation of
manybody
nonequilibrium
dynamics in a
FermiHubbard
model 
(Host:
Matt Dawber)


Identifying
and
understanding
realistic
applications
of noisyÂ
intermediate
scale quantum
(NISQ) devices
such as
quantum
computers and
neutral atom
quantum
simulators is
a topical
problem. An
area of
research that
involves
problems with
a unique blend
of
computational
complexity and
practical
importance is
quantum
manybody
physics.
Consequently,
these problems
constitute one
of the most
exciting
presentday
applications
of NISQ
devices. In
particular,
the study of
highly
correlated
quantum
manybody
systems, which
is
computationally
very
challenging,
could lead to
the discovery
of new quantum
materials with
profound and
exotic
properties. In
this work, we
show how a
stateoftheart
quantum
simulator can
be used to
mathematically solve
for the
dynamics of a
quantum
manybody
system, which
is beyond the
limits of
existing
classical
computational
methods [1].
We use a
quantum
simulator to
develop a new
efficient
classical
approximation
algorithm for
a manybody
system.
Considering
localized 1D
FermiHubbard
systems, we
use an
approximation
ansatz to
develop a new
numerical
method that
facilitates
efficient
classical
simulations in
such regimes.
The method is
based on
approximations
that are well
suited to
describe
localized
onedimensional
FermiHubbard
systems. Since
this new
method does
not have an
error estimate
and is not
valid in
general, we
use a
neutralatom
FermiHubbard
quantum
simulator with
L_exp = 290
lattice sites
to benchmark
its
performance in
terms of
accuracy and
convergence
for evolution
times up to
700 tunneling
times. We use
the tilted
Fermi Hubbard
model [2] for
the
benchmarking.
Our
approximation
method also
offers novel
insights into
the
microscopic
processes that
lead to the
observed
dynamics.
In the limit
of large
tilts, we
identify these
microscopic
processes. And
show that they
constitute an
effective
Hamiltonian
and we
experimentally
show its
validity [3].
This effective
Hamiltonian
features the
novel
phenomenon of
Hilbert space
fragmentation.
Finally, we
characterise
the manybody
problems that
lie further
outside
the accessible
range of this
new method and
discuss
technical
advancements
to our quantum
simulator that
are necessary
to be able to
simulate them.
[1.] Bharath
Hebbe
Madhusudhana
et. al. PRX
Quantum 2,
040325.
[2.] Sebastian
Scherg et al.
Nature
Communications
12 (1), 18
[3.] Thomas
Kohlert et al.
arXiv:2106.15586




February 16, 2022 (9 AM, Zoom)

Dr.
Yinyu Liu,
Harvard
University

Quantum information
processing
based on spins
in
semiconductor
quantum dots

(Host:
Matt Dawber)


The
field of
Quantum
Information is
of great
excitement in
both
fundamental
physics and
industry. One
promising
platform for
quantum
computing is
gatedefined
quantum dots
in
semiconductors.
The greatest
limiting
factor
currently is
that delicate
quantum states
can lose their
quantum nature
due to
interactions
with their
environment.
Other open
challenges are
to coherently
control
largescale
spin qubits
and develop
methods to
entangle
quantum bits
that are
separated by
significant
distances.
Siliconbased
materials are
promising due
to the long
lifetimes of
electrons’
quantum
states, but
also
challenging
due to the
difficulty in
fabrication
and valley
degeneracy. I
will report a
singlettriplet
qubit with a
qubit gate
that is
assisted by
the valley
states. This
work would
potentially
relax the
design and
fabrication
requirement
for scaling.
Moreover,
strong
coupling
between
electron spins
and photons in
hybrid
circuitQED
architecture
has been
achieved in
this research
field. Quantum
optics,
longdistance
quantum
entanglement,
and
communication
via photons
are promised.
To address
that, I will
present my
project on
indium
arsenate
(InAs) double
quantum dots
(DQD) that are
embedded in
circuitQED
architecture.
We
demonstrated
the direct
evidence of
photon
emission from
a DQD in the
microwave
regime. By
achieving
stimulated
emission from
one DQD in
these works,
we invented a
semiconductor
single atom
maser that can
be tuned in
situ. I
will
demonstrate
that a
semiconductorbased
quantum dot is
a promising
platform for
quantum
information as
well as for
fundamental
physics.




February 17, 2022 (9 AM, Zoom)

Dr.
Ye Wang,
Duke
University

TrappedIon
Quantum
Computing and
DataDriven
Quantum
Approximate
Optimization
Algorithms

(Host:
Matt Dawber)


Quantum
computing is
expected to
deliver
exponential
speedup over
classical
computing on
various
computational
tasks such as
quantum
simulation,number
factoring and
solving linear
systems of
equations. But
practical
implementations
of these
quantum
algorithms
demand
nearperfect
qubit
operations.This
talk will
introduce my
work to
mitigate
errors in
trappedion
systems atboth
gate and
circuit
levels. Topics
include the
demonstration
of
highfidelity
entangling
gates in an
ion chain,
hiddeninverse
error
mitigation in
quantum
circuits,
crosstalk
suppression
with local
controls, and
dephasingnoiseoptimized
robust
entangling
gates. These
efforts allow
us to identify
key hardware
upgrades and
push the
system to
reach the
quantum
advantage and
faulttolerant
quantum
computing
requirement.The
second part of
this talk will
introduce our
recent
progress on
the quantum
approximate
optimization
algorithm
(QAOA)
implemented in
a
cyberphysical
power system
to help
resilience.
Our heuristic
strategy
extends the
previews work
(arXiv:1812.04170
(2018)) to
show the
parameter
transferability
between random
weighted
graphs. We
show that our
datadriven
QAOA could
outperform the
GoemansWilliamson
algorithm for
some 24vertex
random
weighted
graphs with a
realistic
noise model in
the current
quantum
processors.
Our work shows
the great
potential of
heuristic
approaches on
Variational
Quantum
Algorithms,
which may be
one of the
most promising
early
candidates for
achieving
quantum
advantage on
NISQ systems




February 21,
2022 (9 AM,
Zoom)

Dr.
Alisa
Javadi,
University
of Basel

Harnessing
LightMatter
Interaction
for Photonic
Quantum
Technologies

(Host:
Matt Dawber)


Photonic
quantum
technologies
have a unique
potential for
applications
such as
largescale
quantum
networks and
quantumenhanced
sensing.
Furthermore,
photons
provide new
paradigms for
quantum
simulations
and a testbed
for
benchmarking
the advantage
of quantum
simulators
over classical
ones. These
applications
demand novel
resources
suchas
efficient
singlephoton
sources,
clusters of
entangled
photons, and
nonlinear
optical gates.
At the current
stage,
solidstate
quantum optics
can strongly
impact
photonic
quantum
information
processing.Solidstate
quantum
emitters can
generate the
necessary
single photons
and more
sophisticated
cluster states
deterministically,
currently
posing a
significant
bottleneck for
photonic
quantum
information
processing. In
this talk, I
will discuss
our progress
in realizing
some of these
elements using
solidstate
quantum
emitters. In
the first
part, I will
present an
efficient
source of
indistinguishable
single photons
[1]. I will
show that we
achieve an
endefficiency
of 57 %, 2.3
times higher
than the
stateoftheart,
and discuss
the
significance
of this
improvement
for photonic
quantum
technologies.In
the second
part, I will
present our
recent
progress in
developing a
scalable
platform for
quantum
photonics. I
will show that
we can
generate
highly
coherent
photons from
GaAs quantum
dots [2].
Furthermore, I
will show that
photons
emitted by
remote GaAs
quantum dots
exhibit
excellent
quantum
interference,
laying the
foundations
for scalable
quantum
photonics. At
the end of my
talk, I will
give an
overview of my
future
research
direction and
my vision for
quantum
computing and
quantum
networking
using optical
photons.
[1] Tomm,
Javadi,
Antoniadis,
Najer, Löbl,
Korsch,
Schott,Valentin,
Wieck, Ludwig,
Warburton, “A
bright and
fast source of
coherentsingle
photons”, Nat.
Nanotechnol.
16,399 (2021).
[2] Zhai,
Nguyen,
Spinnler,Ritzmann,
Löbl, Wieck,
Ludwig,
Javadi,
Warburton,
“Quantum
Interferenceof
Identical
Photons from
Remote Quantum
Dots”,
arXiv:2106.03871
(2021).




February 21, 2022

Prof.
Murray Holland,
JILA, University
of Colorado
Boulder

Using
Machine
Learning for
the Quantum
Design of a
MatterWave
Interferometer

(Host:
Hal Metcalf)


In
this talk, I
will discuss
the
application of
machine
learning for
the design of
an inertial
measurement
device capable
of measuring
accelerations
and rotations
with extreme
sensitivity.
The system
this is based
on consists of
ultracold
atoms in an
optical
lattice
potential
created by
interfering
laser beams.
Our approach
uses
reinforcement
learning, a
branch of
machine
learning that
allows us to
generate
specific
protocols
needed to
realize
latticebased
analogs of
optical
components
including a
beam splitter,
a mirror, and
a recombiner.
The
performance of
these
components can
be evaluated
by comparison
with their
optical
analogs, and
the machine
learned
protocols are
found to offer
significant
advantages.
The resulting
interferometer's
sensitivity
surpasses that
of standard
Bragg
interferometry,
demonstrating
a rich future
potential for
this type of
design
methodology.




February
22, 2022
(Colloquium)

Prof.
Murray Holland
JILA,
University
of Colorado Boulder

Extreme
sensing,
clocks, and
squeezing
atoms and
molecules with
light

(Host:
Hal Metcalf)


I will describe recent ideas for lowering
the
temperature of
ensembles of
ultracold
atoms and
molecules into
the extreme
quantum
regime, for
using
interactions
to entangle
atoms and
molecules into
nonclassical
quantum
states, and
for using
these
nonclassical
states to
realize
quantum
advantages for
metrology,
clocks, and
matterwave
interferometry.
One such topic
is a new
experimentally
demonstrated
idea for laser
cooling by
Sawtooth Wave
Adiabatic
Passage
(SWAP). This
is mostly
relevant to
atoms and
molecules that
possess narrow
linewidth
transitions,
such as the
ultranarrow
clock
transitions,
and promises
to be an
important
extension to
the toolbox of
AMO physics
for laser
cooling and
trapping. We
are exploring
ways to use
optical
cavities and
cavitymediated
interactions
to entangle
atoms so that
we may improve
optical clock
performance,
make repeated
quantum
measurements
beyond the
standard
quantum limit,
and
continuously
track squeezed
quantum
phases. These
approaches
take full
advantage of
the powerful
combination of
the extreme
optical
coherence that
is possible
using atomic
clocks, with
the rich
possibilities
offered by
manybody
physics that
arises when
the atoms
interact
strongly.
Atomic clocks
have already
progressed to
the point that
understanding
how to take
advantage of
quantum
effects will
be crucial in
order to
progress to
the next
generation of
devices.




February 25,
2022 (9 AM,
Zoom)

Dr.
Nathan Schine,
University
of Colorado
Boulder

Quantum
Science with
Photons and
Atoms

(Host:
Matt Dawber)


Can
a material be
made of light?
Can quantum
mechanics help
us measure
time? These
are two
questions in
quantum
science that I
directly
address using
the tools of
atomic physics
and quantum
optics. We
first explore
the
requirements
to make a
quantum Hall
material made
of light. We
trap photons
inside of a
curvedmirror
nonplanar
optical
resonator to
confine the
transverse
motion of
photons and
imbue them
with an
effective mass
and an
effective
magnetic field
for photons.
We add strong
repulsive
interactions
by hybridizing
resonator
photons with
Rydberg
excitations of
a cold atomic
gas, and we
observe the
formation of
the ground
state of
highly
correlated
topological
matter made of
light. We next
turn to a
broad effort
in quantum
science—to
help us to
compute more
efficiently
and to measure
the world more
precisely. In
an
opticaltweezertrapped
array of
strontium
atoms, we
leverage
recent ideas
developed in
quantum
information
processing for
related
metrological
goals. We
demonstrate
nearly a
minute of
atomic
coherence on
an
opticalfrequency
clock
transition. We
then generate
metrologically
useful
entanglement
between
clocktransition
qubits using
Rydberg
excitations,
and we show
that this
entanglement
persists for
approximately
four seconds.
Beyond
enabling
quantumenhanced
optical
clocks, this
work opens the
door to
studies of
interacting
spin and
Hubbard
models,
efficient
computing
architectures,
and database
search
algorithms.




February 28, 2022 (9 AM, Zoom)

Dr.
Alexander
Burgers,
Princeton
University

Advancing
Quantum
Science with
Ytterbium Atom
Arrays

(Host:
Matt Dawber)


Neutral
atom arrays
are a rapidly
developing
platform for
quantum
science.
Rydbergmediated
entanglement
between atoms
has led to
numerous
advances in
quantum
computing and
quantum
simulation
using this
platform. An
emerging
frontier
within this
field is the
use of
alkaline
earthlike
atoms (AEAs)
such as
ytterbium
(Yb). The rich
internal
structure of
these atoms
affords
numerous
unique
capabilities,
including
efficient
Doppler
cooling,
optical clock
transitions
for metrology
applications,
efficient
control of
Rydberg gate
operations
using light
shifts from
ion core
transitions,
and the
capability to
encode qubits
in the nuclear
spin of the J
= 0 electronic
ground state
of fermionic
AEA isotopes.
In this talk I
will describe
our
experimental
platform for
trapping and
manipulating
Yb atoms in
optical
tweezer
arrays. I will
discuss our
recent results
utilizing
transitions in
the Yb+ion
core to
generate light
shifts that
control
excitations to
the Rydberg
state, which
can be used
for efficient
local control
of quantum
gate
operations
[1]. I will
then present
our work
demonstrating
a universal
set of quantum
gate
operations,
including
twoqubit
gates through
the Rydberg
state, using
qubits encoded
in the nuclear
spin of171Yb
[2]. We
observe long
qubit
coherence
times, T2* =
1.24 s, as
well as
highfidelity
singlequbit
operations,
F1Q = 0.99959.
These results
mark the first
such
demonstration
of a universal
set of quantum
gates for
nuclear qubits
in AEAs and
lay the
foundation for
scalable
quantum
computing
architectures
with Yb atom
arrays.
[1] A P
Burgers et al.
arXiv:
2110.06902
(2021)
[2] S Ma*, A P
Burgers* et
al. arXiv:
2112.06799
(2021)




March 1, 2022 (9 AM, Zoom)

Dr.
Erhan
Saglamyurek,
University
of Alberta

Engineering
photonmatter
interfaces for
quantum
networks

(Host:
Matt Dawber)


TThe
realization of
a future
quantum
Internet
relies on
processing and
storage of
quantum
information at
local nodes
and
interconnecting
distant nodes
using photons
[1].
Photonmatter
interfaces
constitute
building
blocks for
such networks,
allowing
reversible
transfer of
quantum
information
between
“stationary”
atoms and
“flying”
photons.
Despite
impressive
progress over
the past two
decades,
practical
realizations
of
photonmatter
quantum
interfaces
still face a
lot of
challenges. In
my talk, I
will address
these
challenges in
view of
requirements
of largescale
quantum
networks, and
present our
experimental
efforts
towards
overcoming
them.
Particularly,
I will focus
on integrated
lightmatter
interfaces
based on
rareearth ion
doped solids,
and show our
demonstrations
including the
storage of
photonic
entanglement
in these
devices [24].
Furthermore, I
will present a
novel approach
to develop a
broadband
spinphoton
interface for
longlived
storage and
manipulation
of light along
with the
proofofprinciple
implementations
of this
technique in
an ensemble of
lasercooled
atoms [5] and
a
BoseEinstein
condensate
[6]. Finally,
I will discuss
my ongoing
research and
future plans
towards
building
quantum
networks and
potential
applications,
including
distributed
and modular
quantum
computing, and
remote quantum
sensing.
1. H. J.
Kimble.
Nature, 453
10231030
(2008).
2. E.
Saglamyurek et
al. Nature
469, 512515,
(2011).
3. E.
Saglamyurek et
al. Nature
Photonics 9,
8387 (2015).
4. E.
Saglamyurek et
al. Nature
Communications
7, 11202
(2016).
5. E.
Saglamyurek et
al. Nature
Photonics 12,
774782
(2018).
6. E.
Saglamyurek et
al. New
Journal of
Physics 23,
043028 (2021).




March 2, 2022 (9 AM, Zoom)

Dr.
Pankaj Jha,
Caltech

Engineering
Defects in
Flatland for
Quantum
Information
Science and
Technologies

(Host:
Matt Dawber)


Single photon
sources (SPSs)
are one of the
building
blocks for
quantum
technologies,
including
optical
quantum
computing,
quantum
communications,
and sensing
and metrology.
In the past
two decades,
various
systems have
been explored,
including
heralded SPSs,
atoms and
atomlike
systems as
quantum
emitters, and
highly
attenuated
lasers.
However, both
fundamental
and
technological
challenges
need to be
resolved to
achieve a
reliable SPS
which is
scalable and
capable of
generating
single photons
on demand with
high purity,
indistinguishability,
and repetition
rate.
In this
seminar, I
will highlight
atomic defects
(also known as
color centers)
in van der
Waals crystals
of
widebandgap
material such
as hexagonal
boron nitride
(hBN) as a
promising
candidate for
quantum light
sources owing
to its
enticing
properties,
such as high
stability and
brightness
from cryogenic
temperatures
to 800 K,
convenient
integration
with flexible
substrates,
fiber optics,
and onchip
photonic
devices. In
the first part
of the talk, I
will address
two
fundamental
questions
about hBN
color centers:
(1) Where are
these color
centers
located in any
multilayered
flake and (2)
What is the
orientation of
their dipole
moment?
I will show
our
experimental
results on
nanometric
axial
localization
(down to ~7
nm) of these
color centers
with
3Dcharacterization
of their
dipole
orientation
using the
phase change
material,vanadium
dioxide.
In the second
part of my
talk, I will
discuss our
ongoing work
which utilizes
these color
centers as a
quantum module
for photon
addition
quantum
technology,
applied to the
interferometric
imaging, LIDAR
enhancement
for
astronomical,
military, and
other
applications.
Finally, I
will conclude
by presenting
my vision for
this quantum
hardware
platform,
outlining its
usages,including
metrology of
single photon
detectors,
generation of
intensity
squeezed light
at room
temperature as
well as
interfacing
machine
learning with
quantum
information
for
intelligent
light
detection and
characterization.




March 28, 2022

Prof.
Daniel Rolles,
Kansas State
University

Gasphase
photochemistry
studies with
freeelectron
lasers

(Host:
Tom Weinacht)


Xray
freeelectron
lasers provide
intense,
shortpulse,
shortwavelength
radiation that
can be used to
study
ultrafast
electronic and
structural
dynamics in
gasphase
molecules with
unprecedented
spatial and
temporal
resolution. I
will present
recent
examples of
experiments
utilizing a
variety of
different
techniques
such as
timeresolved
photoelectron
spectroscopy
[1] and
Coulomb
explosion
imaging [2,3].
The results
are compared
to similar
experiments
performed with
other
ultrafast
techniques
such as
ultrafast
electron
diffraction
and
strongfield
ionization
based experiments
with
nearinfrared
laser sources
in order to
highlight
strengths and
limitations of
each
technique.
References
[1] S. Pathak
et al., Nat.
Chem. 12,
795 (2020)
[2] R. Boll et
al., Nat.
Phys. (2022); doi.org/10.1038/s41567022015070
[3] S. Pathak
et al., J.
Phys. Chem.
Lett. 11,
10205 (2020)




March 30, 2022

Prof.
Kyung
Soo Choi (SBU
2006),
University of
Waterloo

Manybody
QED with atoms
and photons

(Host:
Hal Metcalf)


An
exciting
frontier in
quantum
information
science is the
creation and
manipulation
of quantum
systems that
are built and
controlled
quanta by
quanta. In
this context,
there is
active
research
worldwide to
achieve strong
and coherent
coupling
between light
and matter as
the building
block of
complex
quantum
systems.
Despite the
range of
physical
behaviors
accessible by
these QED
systems, the
lowenergy
description is
often masked
by small
fluctuations
around the
mean fields.
In contrast,
we describe
our
theory/experimental
program
towards novel
forms of
lightmatter
quantum
systems, where
a
highlycorrelated
Rydberg
quantum
material is
strongly
coupled to a
cavity field.
We call this
new domain of
strong
coupling
quantum
optics,
"manybody
quantum
electrodynamics."
I describe our
laboratory
efforts
towards the
exploration of
new physics in
this uncharted
territory,
where
locallygauged
quantum
materials are
entirely
driven by the
QED vacuum. We
find that
genuinely
surprising
phenomena
arise from the
universal
features of
nonperturbative
physics of
manybody QED,
including the
stabilization
of topological
spin liquids
and
selfcorrecting
quantum
memories.




April 18, 2022

Prof.
Viatcheslav
Kokoouline,
University
of Central
Florida

Recent
progress in
theoretical
description of
excitation and
dissociative
processes in
collisions of
electrons with
molecular ions

(Host:
Jesús Pérez
Ríos)


The
talk gives a
short overview
of recent
progress in
successful
theoretical
description of
various
processes
taken place in collisions
of electrons
with molecular
ions at
energies below
a few eV:
dissociative
recombination,
rotational,
vibrational,
and electronic
excitation of
the ions,
molecular
photoionization.
The theory
based on first
principles
only (and,
sometimes,
heavy
numerical
calculations)
is now able to
give reliable
cross sections
for these
processes for
ions having
up to
approximately
10 atoms. The
progress in
the
theoretical
description of
the processes
is crucial for
various
applications
where
molecular
plasma is
involved.




June 3, 2022

Prof.
Emily Grace,
Northwestern
College

Building
the Island
Cure: Iowa
Stony Brook
Lasers ANd DNA
CourseBased
Undergraduate
Research
Experience

(Host:
Eric Jones)


ISLAND
CURE is a new
collaborative
project that
uses
multidisciplinary
approaches in
science
experimental
design and
science
pedagogy. This
collaborative
interdisciplinary
CURE project
includes
faculty and
students from
the physics,
chemistry, and
biology
departments at
Northwestern
College (NWC)
and the Laser
Teaching
Center (LTC)
at Stony Brook
University.
Comparisons
will be made
between NWC
and LTC
students who
seek out
independent
research
experiences,
students
enrolled in a
class with a
"cookbook" lab
versus a
CUREbased lab
component.
ISLAND CURE
will have a
central focus
on using optical
methods
to measure
biochemical
processes.
Students will
engage in
original
research
involving
cuttingedge
and relevant
technologies
(e.g., optical
tweezing, DNA
cloning, and
protein
expression).
The research
goals include
(1)
understanding
how to use
CURE methods
to guide
students in
developing the
skills needed
to effectively
engage in
scientific
practices in
physics,
chemistry, and
biology, (2)
comparing the
outcomes of
CURE students
to traditional
independent
student
project
results, and
(3) exploring
the impact and
sustainability
of CURE
scholarship
for faculty at
small
colleges. This
talk will lay
out the
development of
this
collaboration,
and present
progress.




June 20, 2022

Dr.
Ruaridh
Forbes,
SLAC

Sensitivity
of Xray
photoelectron
spectroscopy
and Coulomb
explosion
imaging to
excited state
dynamics in
polyatomic
molecules

(Host:
Tom Weinacht)


The
UV
photochemistry
of gasphase
CS_{2}
exhibits many
general
features of
complex
excited state
dynamics:
vibrational
mode coupling,
internal
conversion,
intersystem
crossing, and
dissociation.
The molecule
initially
undergoes
bending and
symmetric
stretching
motion before
coupling to
asymmetric
stretch motion
leading to
dissociation
of atomic
sulfur. In
this talk, I
will explore
the ability of
timeresolved
Xray
photoelectron
spectroscopy
and Coulomb
explosion
imaging, at
the sulfur 2p
site, to
investigate
such complex
photodynamics.
The results of
a 200 nm UV
pump + 180 eV
soft Xray
probe
experiment at
the FLASH
freeelectron
laser (FEL)
will be
presented. By
utilizing a
soft Xray
probe
ionization at
S 2p edge
(~170 eV
binding
energy) can be
performed
providing a
site selective
view on the
photoinduced
dynamics. Ions
and electrons
following
ionization
were
simultaneously
collected in a
doublesided
velocity map
imaging (VMI)
instrument.
The momenta of
the
Coulombexploded
ions probed
the molecular
geometry at
the time of
ionization,
while the
measured
photoelectrons
yielded
information
about the
evolving
electronic and
nuclear
structure
through shifts
in the S 2p
binding
energy.
The low
repetition
rate, high
count rate
experimental
conditions
prevent the
use of
coincidence
techniques to
separate
overlapping
contributions
to the
photoelectron
spectrum from
the various
ionization
channels. To
overcome this,
we have
employed
electronion
covariance to
associate
sulfur 2p
binding energy
shifts to
particular
ionization
channels and
molecular
geometries. We
find a sulfur
2p binding
energy shift
of ~2 eV in
covariance
with
lowmomentum S^{2+}
associated
with
dissociated
atomic sulfur,
and a
transient
enhancement in
the production
of
highermomentum
S^{+}
ions following
photoexcitation
and an
associated
broadening of
the covariance
photoelectron
spectrum,
indicating
some effect on
the corelevel
chemical shift
from either
the
photoexcitation
or the
vibrational
motion prior
to
photodissociation.
Our
experimental
results are
supported by
simulations of
the neutral CS_{2}
photodynamics
and core
ionization.
Preliminary
results on the
use of
electronphoton
covariances to
achieve
subbandwidth
spectral
resolution
will also be
presented.
These result
pave the way
for performing
highresolution
electron
spectroscopy
measurements
at SASE FEL
despite the
inherently
large (several
eV) bandwidths
of these
machines.




July 6, 2022 (10:30 AM)

Dr.
Dan Herman
NIST,
University
of Colorado,
Boulder

Applications
of Deployable
OpenPath
Infrared
DualComb
Spectrometers

(Host:
Tom Allison)


Dual
frequency comb
spectroscopy
(DCS) is an
emerging
technique that
achieves high
spectral
resolution
across wide
optical
bandwidths. In
this talk, I
will summarize
the
development of
portable,
remotecontrolled,
openpath DCS
systems for
measurement in
the
nearinfrared
and
midinfrared
spectral
regions. I
will also
examine
several
applications
where the
benefits of
the DCS
technique are
highlighted,
including
calibrationfree
agricultural
gas flux
quantification,
greenhouse gas
source
attribution,
and air
quality
monitoring.




