8 16.00 90 232.0 92 238.0 17 35.45 68 167.3 53 126.9 & 62 150.4 10.81 5 32.1 16 57 138.9 DETECTION AND CHARACTERIZATION OF THE STANNYLENE (SnH2) FREE RADICAL IN THE GAS PHASE TONY C. SMITH, Ideal Vacuum Products, LLC, Albuquerque, NM DENNIS J. CLOUTHIER, Department of Chemistry, University of Kentucky, Lexington, KY

TIN: 7 MAJOR AND 3 MINOR (<1%) ISOTOPES In fact, Tin has the most stable isotopes of all elements! Xenon is next with 8 stable isotopes, followed by Cadmium and Tellurium, with 6 each. The spectra of Tin containing molecules can be complicated by isotope splittings.

SnH2 and SnD2 are unknown in the gas phase! EXPERIMENTAL BACKGROUND 1. Infrared Spectra of the Novel Sn2H2 Species and the Reactive SnH1,2,3 and PbH1,2,3 Intermediates in Solid Neon, Deuterium, and Argon, Xuefeng Wang, Lester Andrews, George Chertihin, P. F. Souter, J. Phys. Chem. A 106, 6302 (2002). (Laser ablation studies of tin and lead and their reactions with hydrogen studied by IR matrix spectroscopy) SnH2 and SnD2 are unknown in the gas phase!

MO PICTURE ↑↓ b1 n(Sn 5px) n(lone pair) b2 (Sn-H) (bonding) a1 90o <H-Sn-H 180o ↑↓ a1 b2 b1

Geometries: B3LYP/aug-cc-pVTZ-pp AB INITIO POTENTIALS Geometries: B3LYP/aug-cc-pVTZ-pp Barrier To Linearity ~ 8000 cm-1

SnH2 SYNTHESIS FOR JET SPECTROSCOPY Sn(CH3)4 or SnH4 + Argon

TETRAMETHYL TIN YIELDS NEW SPECTRA IN THE DCM REGION

LIF SPECTRA FROM SnH4 & SnD4 in the DCM REGION

SnD2 LIF SPECTRA 20 2 Sn2 Sn2 Sn2 3 20

0-0 BAND LIF SPECTRUM OF SnH2 All transitions to lowest Ka= 0 levels in the excited state.

Transitions to Ka = 1 much weaker than expected SnD2 0-0 BAND LIF SPECTRUM ANALYSIS Transitions to Ka = 1 much weaker than expected

RESOLUTION OF THE TIN ISOTOPES

Long bending progressions as expected for a large change in bond angle EMISSION SPECTRA Long bending progressions as expected for a large change in bond angle

FLUORESCENCE LIFETIMES 240 ns 20,2 Rotational Energy 670 ns 10,1 1350 ns 00,0 Fluorescence lifetimes decrease rapidly with increasing rotational energy

HOLE BURNING TO PROBE DARK ROVIBRONIC STATES Dark State Bright State Fluorescence Intensity l Probe Laser Ground State Probe Pump

HOLE BURNING SPECTRA Pump Laser Probe Laser LIF

rR1(1) HOLE BURNING SPECTRA & 220 LIFETIMES V2=0 V2=1 V2=2 6 ps 4 ps 2 ps 𝟎 𝟎 𝟎 𝑩𝒂𝒏𝒅 𝟐 𝟎 𝟏 𝑩𝒂𝒏𝒅 𝟐 𝟎 𝟐 𝑩𝒂𝒏𝒅 220 fluorescence lifetimes decrease rapidly with increasing vibrational energy

MOLECULAR STRUCTURES B 1B1 X 1A1 ~ 1.738(5) Å 123.0(3) ~ 1.774(3) Å 91.0(2)

PREDISSOCIATION MECHANISM

CONCLUSIONS SnH2 and SnD2 have been observed in the gas phase. SnH4 readily dissociates in an electric discharge to produce SnH2. LIF spectra show that SnH2 is rotationally predissociated in the excited state. Rotational analysis and hole burning expts. were used to derive rotational constants. The r0 molecular structure of the stannylene radical has been determined for both states.