ASTROCHEMISTRY &

HYPERSONIC CHEMISTRYTaylor Copeland

The Savin Group

Nevis Laboratories, Summer 2017

Overview

Astrochemistry

Protostellar formation

Merged beams

experiment

Hypersonic Chemistry

Atmospheric reentry

Nitrogen ionization

Overview

Astrochemistry

Protostellar formation

Merged beams

experiment

Hypersonic Chemistry

Atmospheric reentry

Nitrogen ionization

Astrochemistry

Formation of stars,

planets, life from

interstellar clouds

Diffuse clouds of atoms

Dense clouds of

molecules, ions

Protostellar

cores

Chemistry in protostellar cores

Chemistry in protostellar cores

Atoms (ions) and

molecules freeze onto dust grains, except H3

+

Dominant charge carriers are H3

+ isotopologues

Only H2D+ and D2H

+ emit

for cool gases (below 20 K)

Ionization fraction of H3+

affects collapse of cloud

Determine ionization fraction from H3

+

isotopologues

D2H+, H2D

+

Uncertainties in

deuterating gas-phase

reactions

D + H3+ → H2D

+ + H

Overview

Astrochemistry

Protostellar formation

Merged beams

experiment

Hypersonic Chemistry

Atmospheric reentry

Nitrogen ionization

Merged Beams Experiment

D + H3+ → H2D

+ + H

Plasma sources

Evacuated beam line

Electrostatic optics

Photodetachment

Beam transmission

Maintaining a vaccum

Scroll pumps

Intake

Exhaust

Beam pipe alignment

Pierre

Hollenbrand

Kyle

Bowen

Dr Daniel

SavinMe

Overview

Astrochemistry

Protostellar formation

Merged beams

experiment

Hypersonic Chemistry

Atmospheric reentry

Nitrogen ionization

Hypersonic Chemistry

Atmospheric reentry

Mach 5 and up

High temperatures

Plasma flow

Electron-impact ionization

N + e− ⟶N+ + e− + e−

Radiative heating of reentry vehicle

Electron-Impact Ionization

Cross sections from binary-encounter Bethe (BEB)

theory

Need binding & orbital energies from Hartree-Fock

wavefunction solutions

𝜎BEB 𝑛ℓ =4 𝜋a0

2

𝑡 + (𝑢 + 1)

R

𝐵

2ln 𝑡

21 −

1

𝑡2+ 1 −

1

𝑡+ln 𝑡

1 + 𝑡

𝐵 = binding energy 𝑢 = orbital energy 𝑡 = translational energy

R = Rydberg energy a0 = Bohr radius

Nitrogen EI cross sections

Reaction Rate Coefficients

Numerical integrations

Precision/accuracy

𝛼 𝑇 = නEmin

∞

𝜎 𝑣 𝐹 𝐸, 𝑇 𝑑𝐸

𝑑 N+

𝑑𝑡= −𝛼 N+ [e−]

Models for rate coefficients

Arrhenius-Kooij Model

Curve fitting

Model for rate coefficients

𝛼AK 𝑇 = A 𝑇B exp − ΤC 𝑇

𝛼 𝑇 = නEmin

∞

𝜎 𝑣 𝐹 𝐸, 𝑇 𝑑𝐸

Fitted model agreements

Chris

Ciccarino

Dr Daniel

Savin

Me

Summary / Looking forward

Further data collection for deuterium reactions

in merged beams experiment

Have a viable method for determining EII rate

coefficients

Need EII data for oxygen

Thanks to John Parsons, Georgia Karagiorgi,

Amy Garwood, the REU program and the NSF

Thank you Nevis!

Questions?